WO2016120276A1

WO2016120276A1 - Methods and devices for detecting surface contamination by particles in free air

Info

Publication number: WO2016120276A1
Application number: PCT/EP2016/051584
Authority: WO
Inventors: Ludovic Escoubas; Olivier Palais; Marcel Laurent PASQUINELLI; Philippe Godefroy; Daniel Soler; Isabelle TOVENA PECAULT
Original assignee: Aix-Marseille Universite (Amu); Centre National De La Recherche Scientifique (Cnrs)
Priority date: 2015-01-27
Filing date: 2016-01-26
Publication date: 2016-08-04
Also published as: FR3032036B1; FR3032036A1

Abstract

Disclosed are methods and devices for detecting surface contamination by particles in free air. According to one aspect, the present description relates to a device for detecting surface contamination by particles moving in free air. Said device comprises a stationary collection surface (10) for receiving particles on one of the faces (11) thereof, and an optical head (30) which is arranged on the side of the collection surface that is opposite the face (11) for receiving the particles. The optical head comprises an optical imaging system (38) for forming an image of an elementary analysis surface (13i) of the collection surface (10) on a detection surface (33), and a lighting source (34, 35) for emitting at least one lighting beam which is suitable for covering said elementary analysis surface (13i). Means (40) for moving the optical head (30) allow the collection surface (10) to be scanned bidirectionally.

Description

Methods and devices for detecting surface contamination by particles evolving in the open air

STATE OF THE ART Technical field The present description relates to methods and devices for detecting surface contamination by particles evolving in free air. It applies in particular to the detection of sedimented particles in areas with controlled environment or the control of air pollution.

State of the art In many industrial sectors (micro or nanoelectronics, optics, opto-mechanics, photonics, micromechanics) and health, the control of the environment has become a strategic issue. Classification standards and standards are evolving and thus creating new needs to adapt to increasingly demanding requirements.

Clean rooms, and more generally controlled environment areas (hereinafter ZECs), also referred to as "Zones with Related Mastery Environment" (ZEMA), are classified according to the number of volume particles for sizes between 0, 1 μιη and 5 μιη according to ISO 14644-1. A new international standard ISO 14644-9 for classifying the particulate cleanliness of surfaces has just been approved: the surface particulate contaminants that are considered are those whose unit size is generally between 0.05μιη and 500μιη for the needs classification.

Optimization of the airspace ZEC (filtration, air circuit and indoor air mixing rate) allows to eliminate and control the volume concentrations of particles of smaller size or order micron (μιη). It appears that certain operations (manufacture, assembly, maintenance) carried out inside ZEC induce an increase in the quantity of particulate contaminants with a spectrum of size that can be very large, of which the largest (greater than the μιη) can not be controlled and eliminated by the aeronautics of these ZECs. In fact, particles larger than one micron are deposited, or in other words, settle very rapidly on the surfaces of the ZEC and can not be eliminated by the air flows. Therefore, there is a need for the detection and analysis of sedimented particles. Recommendations for sedimentation and particle counting methods and apparatus are made according to ISO 14644-3. Indeed, sedimentation tests are the only means of analysis known to date that is effective in guaranteeing the ZEC user that there is no unacceptable contamination in the ZEC following the operations carried out within it. . The tests generally consist in recovering the particles deposited by sedimentation, whatever their orientation, from the so-called "control plates", then quantifying them in number or mass or measuring their effects (light scattering). or covered area).

The disadvantages of the sedimentation tests as they are carried out to date are numerous. They impose the collection and transport to the counting apparatus of the control plates positioned at the appropriate places in the ZEC. During this transport, there may be a loss of the sedimented particles, especially for those with the largest size, which by nature are the least adherent to the control plates, with the risk of seeing the surface contamination counted less than the reality . During transport to the counting device of all these control plates, it can also occur on contamination of these plates if the packaging of these plates is not itself clean and sealed. In other words, the sedimentation tests carried out according to ISO 14644-3 are long, tedious and not necessarily completely reliable.

Several sedimented particulate contamination measurement systems exist that make it possible to limit the displacement of the collection plates.

For example, systems using pumps for directing particles to any counting system are known. The main problem with this type of system is that the behavior of the particles that must settle is disturbed by the local air flow; the count is not representative of the sedimentation because the environment is disturbed by the measurement system itself.

Various systems are also described allowing the detection of the shadow formed by particles deposited on a detection surface of a sensor (see for example US5218211 patent). These systems, however, require the addition of artificial lighting in the environment that is to be analyzed in order to continue the counting in the dark, which generates risks of disturbance of the environment, in particular because of the possible impact of lighting sources on the airspace near the sensors.

The present description proposes a method and a device for detecting surface contamination by particles evolving in free air, notably allowing identification and counting of particles without displacement of the collection plate and without disturbance of the environment in which the particles evolve.

SUMMARY OF THE INVENTION According to a first aspect, the present description relates to a method of detecting surface contamination by particles evolving in free air in a zone to be controlled.

The zone to be controlled may be a ZEMA closed zone or an open zone for the control of atmospheric pollution.

According to one or more exemplary embodiments, the method comprises:

- the arrangement in the area to be controlled of at least one collection surface, fixed, receiving particles on one of its faces;

for each collection surface, illuminating a region of said collection surface by means of a lighting beam emitted from a light source located in an optical head, said optical head being disposed on the surface side collector opposed to the particle receiving face;

forming an image of an elemental analysis surface of the illuminated region by means of an imaging optical system arranged in the optical head, each particle on the elemental analysis surface emitting a backscattered light signal; moving the optical head to scan along the two directions of the collection surface and at each point of the scan an image of the elemental analysis surface;

image processing of the elemental analysis surfaces acquired at the different points of the scan so as to detect the particles on the entire collection surface.

The method thus described allows a characterization of fast, reliable and low cost surface contamination. In particular, neither the behavior of the particles nor their environment is disturbed during the implementation of the method and the analysis does not require a systematic calibration. The measurement, while being fast, is therefore perfectly representative of surface contamination of the environment, and in particular of surface contamination resulting from sedimentation. In addition, the direct imaging of particles makes it possible to analyze the geometry, size and distribution of pollution.

According to one or more embodiments, the lighting beam is oriented so that the beam resulting from the specular reflection of the illumination beam on the collection surface does not enter the imaging optical system. This gives so-called "black background" images that have a very good contrast of the particles to be detected.

According to one or more exemplary embodiments, the scanning of the optical head is reproducibly made, and so as to form juxtaposed and disjoint elementary analysis surfaces covering the whole of the collection surface, in order to ensure complete coverage of the collection surface, without overlaying the elemental analysis surfaces. For example, the sweep is in the form of a coil.

According to one or more exemplary embodiments, the method comprises, for each formation of an image of an elementary analysis surface, the acquisition of a first image of the elementary analysis surface by means of the optical imaging system with lighting, acquiring a second image of the elemental analysis surface by means of the imaging optical system without illumination, and subtracting the two images to form the image of the elemental analysis surface. These preliminary steps make it possible to limit the noise resulting from ambient lighting.

According to one or more exemplary embodiments, the method comprises, for each image formed of an elementary analysis surface, the estimation of a threshold level and the detection of the points of the image having a higher intensity at the level of threshold for the detection of particles and the determination of their sizes.

According to one or more exemplary embodiments, the method further comprises a temporal tracking of the detected particles, the particles being able to be identified for example according to their number and their sizes, or by the estimation of the surface covered by the particles.

According to one or more exemplary embodiments, a first scan of the collection surface can be carried out before launching the analysis of the surface contamination by the particles, in order to characterize the state of initial pollution of the surface, to the origin of time tracking. This eliminates possible surface defects or cleanliness defects of the collection surface; therefore, the analysis is done by relative counting of the number of particles and does not require a perfectly clean surface or a flawless surface.

According to one or more exemplary embodiments, the method furthermore comprises the setting up of an alarm that triggers beyond a previously chosen threshold of particulate contamination.

According to one or more exemplary embodiments, the method relates to the detection of surface contamination of a controlled environment zone; it includes the detection of surface contamination at different locations in said area. According to a second aspect, the present description relates to a surface contamination detection device adapted to the implementation of the method according to the first aspect.

According to one or more exemplary embodiments, the device according to the present description comprises:

a fixed collecting surface intended to receive particles moving in free air on one of its faces;

an optical head arranged on the opposite side of the collection surface with respect to the particle receiving face and comprising:

an imaging optical system for forming an image of an elemental analysis surface of the collection surface on a detection surface;

a lighting source enabling the emission of at least one lighting beam adapted to cover said elemental analysis surface; means for moving the optical head to scan in both directions of the collection surface and at each point of the scan, forming an image of the elemental analysis surface;

an electronic control unit for processing signals from the imaging optical system.

The collecting surface is transparent at least at the wavelength of the light source. Such a device, while compact, allows reliable analysis of particulate contamination on control test surfaces of a few cm ² to at least one hundred cm ² .

According to one or more exemplary embodiments, the illumination beam is oriented such that the beam resulting from the specular reflection of the illumination beam on the collection surface does not enter the imaging optical system. Such an arrangement allows the formation of so-called "black background" images that allow a very good contrast of the particles to be detected.

According to one or more exemplary embodiments, the lighting source comprises at least two elementary sources arranged on either side of the imaging optical system and whose emission covers said elementary surface. The elementary source or sources are, for example, light-emitting diodes.

According to one or more exemplary embodiments, the imaging optical system comprises an objective and a two-dimensional detector having a detection surface whose dimensions define the dimensions of the elemental analysis surface. The choice of the objective and the resolution of the two-dimensional detector can be made according to the minimum size of the particles to be detected, the collection surface and the time required for the analysis of the collection surface.

According to one or more exemplary embodiments, the imaging optical system comprises a spectral filter adapted to transmit only the emission spectral band of the lighting source. Such a filter makes it possible to let the light backscattered by the particles onto the collection surface while limiting the parasitic light flux coming from the environment.

According to one or more exemplary embodiments, the electronic control unit transmits the signals coming from the imaging optical system to a control unit ensuring all or part of the image processing of the elementary analysis surfaces for the detection of the particles on the whole. from the collecting surface.

According to one or more exemplary embodiments, the surface contamination detection device is autonomous, a processing of the images of the elementary analysis surfaces being made at the level of the electronic control unit.

The present description relates, according to a third aspect, a surface contamination detection system of a controlled environment zone comprising a set of surface contamination detection devices according to the second aspect and a control unit common to these devices. The autonomy of the surface contamination detector according to the present description allows a centralized management of several detectors controlled by the same workstation. The workstation can be deported by network, in the case where the detectors are in different rooms for example.

BRIEF DESCRIPTION OF THE DRAWINGS Other advantages and characteristics of the invention will appear on reading the description, illustrated by the following figures:

FIGS. 1A and 1B, diagrams illustrating a device for detecting surface contamination by particles evolving in free air according to the present description;

FIG. 2, a diagram showing an example of an optical head of a detection device according to the present description;

Figure 3, a representation of the set of elementary analysis surfaces swept on a collecting surface;

4A, 4B and 4C, intensity curves representing an example of a light signal detected when the elementary analysis surface is illuminated, the light signal detected when the elemental analysis surface is not lit, and the curve obtained. by subtracting the previous curves;

5, an image of an elemental analysis surface on which the particles classified according to their sizes are highlighted;

Figure 6, a curve for monitoring contamination over time at a collection surface;

FIG. 7, an example of a system for detecting surface contamination of a controlled environment zone comprising a set of detection devices according to the present description;

8, a diagram showing an example of an arrangement of the surface contamination detection devices in a controlled environment zone. DETAILED DESCRIPTION

In the figures, the identical elements are indicated by the same references.

FIGS. 1A and 1B show an example of a detection device according to the present description, adapted to the detection of surface contamination by particles evolving in free air.

By "particles" or "particulate contaminants" is generally meant in the present description any solid element and / or liquid likely to adhere to the collection surface by physical and / or chemical interactions, excluding films that cover the entire surface, this definition being in accordance with the definition given in ISO 14644-9 (2013). According to one or more examples of the present description, a "particle" or "particulate contaminant" within the meaning of the present description may comprise any element suspended in ambient air sufficiently heavy to be able to settle on a horizontal or inclined surface, typically particles of the order of one micron.

The surface contamination detection device 100 shown in FIGS. 1A and 1B comprises a collection surface 10 and an optronic system 20 for the detection and analysis of particles deposited on the collection surface, for example by sedimentation; the optronic system 20 of the detection device 100 according to this example is connected to a control computer 60 itself connected to a screen 61. The collecting surface is transparent at least at the wavelength of the light source. This is for example a transparent blade, for example glass, on which particles are deposited. The collection surface is advantageously made in a resistant glass (for example silica) in order to be often cleaned without degrading. In this way, the collection surface has the advantage of being able to undergo surface cleaning cycles, like all clean room surfaces, and therefore to be truly representative of the state of cleanliness of the monitored surfaces.

The collection surface has a sufficient flatness so that small particles (typically of the order of one micron) remain focused, that is to say in the depth of field of the imaging system of the optronic system. Typically, we will look for a ratio between the flatness of the surface, defined as the largest gap between a hollow and a bump, and the size of the particles to be detected, less than or equal to 10. For example, for particles of the micron order (or more), it will seek a flatness less than 10 microns, preferably less than one micron.

Moreover, the collection surface advantageously has a minimum of surface defects; however, as will be described later, an initial calibration of the detector may make it possible to work with collection surfaces that are not perfectly clean or that have surface defects.

The collection surface 10 comprises a receiving face 11 or "upper face" on which particulate contaminants (referenced PI, P2 in FIG. 1A) are deposited and a face 12 opposite to the collection face 11 or "lower face" of the the side of which is the optronic system 20. Although in the figures, the collection surface is shown substantially horizontal when the detection device is in use, it is quite possible to work with the collection surface arranged in an inclined plane or even vertical, in order to obtain representative analyzes of the surface contamination of inclined surfaces.

The surface area of the collection surface, to be representative of the state of cleanliness of the monitored surfaces, is, according to an exemplary embodiment, greater than a few cm ² , for example of the order of ten or a few dozen cm ² , or up to 100 cm ² (area considered in the standard IEST 1246 E used until now in the characterization of the surface particle contamination).

In practice, the total analyzable surface, determined as the collection surface of a detector or the collection surfaces added with N detectors, results from a compromise between the smallest particle size to be detected, the time required for the analysis. , the environment to be monitored and / or the target areas to be controlled. The optronic system 20 comprises an optical head 30 for illuminating and imaging an elemental analysis surface 13; on a detection surface of the optical head. An example of an optical head is described in more detail in FIG. 2. The optoelectronic system also comprises means 40 for moving the optical head 30 making it possible to scan the entire collection surface 10; the displacement means comprise for example translation rails 41, 42 for moving the optical head 30 in two perpendicular directions. Advantageously, the displacement means allow a reproducible scan of the collection surface, that is to say that from one scan to another, the same elemental analysis surfaces are imaged, which allows more robust calibrations. of the detection device.

The optoelectronic system furthermore comprises an electronic control unit 50 integrated into the body of the detection device and which communicates with the control computer 60 equipped with control software.

The electronic control unit 50 makes it possible, for example, to drive the translation motors of the rails 41, 42 in order to scan the collection surface. The electronic control unit also provides, in a variant, all or part of the real-time processing of the images acquired by the optical head. The electronic control unit can also be used to manage the initialization of the detection device, to adjust the acquisition (resolution, lighting, etc.), to set up contamination thresholds at which a warning threshold can be triggered. . According to one variant, the electronic control unit can also allow the self-calibration of the optical head on the order of the control computer after cleaning to avoid taking into account the permanent defects on the collection surface such as scratches.

The control computer 60, equipped with a control software, can make it possible to control the optronic system 20, to display the acquisitions of the optronic system on the screen 61 and, according to variants, to carry out the analysis in real time or a posteriori of the images formed by the detection device or the set of detection devices when a plurality of them are arranged in a network.

FIG. 2 illustrates an example of optical head 30 of a detection device according to the present description. The optical head 30 includes a light source for illuminating a region of the collection surface 10 and an imaging optical system 38 for forming an image of an elemental analysis surface 13; of the collection surface 10 on a detection surface 33.

The illumination is adapted to illuminate a region covering the instantaneous analysis surface 13; The light source comprises, in the example of Figure 2, two sources elements 34, 35 located on either side of the imaging optical system 38 and oriented to prevent the light beams emitted by the elementary sources and reflected by the lower face2 and the upper face 11 of the collection surface are reinjected in the imaging optical system. This arrangement of elementary sources allows a so-called "black background"imaging; indeed the light directly reflected by the collection surface is not detected; it is only when there is the presence of a particle capable of backscattering light in the imaging optical system that a light signal can be detected on the detection surface 33.

The light source may advantageously comprise one or more elemental sources emitting in the UV, the visible or the infrared, for example light emitting diodes.

The imaging optical system 38 comprises according to one or more exemplary embodiments an optical objective 31, formed of one or more optical lenses, and a two-dimensional optical detector 32, the objective allowing the optical conjugation between the detection surface of the optical detector 32. and the elemental analysis surface 13;

The optical objective has a numerical aperture adapted to the size of the particles that one seeks to detect. For example, for the detection of particles of the order of 5 μιη, it will be possible to work with an objective open at f / 4 (for a working wavelength of 532 nm).

The two-dimensional optical detector 32 is for example a CCD or CMOS camera having for example a rectangular detection surface 33 formed of elementary detectors or "pixels", advantageously at least 10 ⁵ pixels. Typically this sensor can allow a resolution of 5μιη on a surface of 4 x 5 mm ² approximately. By moving the optical head, it is possible to cover a total area of analysis whose surface is 100 cm ² or more.

The imaging optical system 38 may also comprise, according to an example, an optical filter 36 adapted to the wavelength of the illumination source in order to filter the parasitic light rays and to optimize the optical signal-to-noise ratio.

A surface contamination detection device as illustrated by means of FIGS. 1A, 1B and 2 has the advantage of a very compact ergonomics; for example the detection device may have dimensions smaller than 20 cm in each of the two directions.

FIG. 3 represents, in one example, the scanning of the collection surface 10. The instantaneous analysis surface 13; is translated serpentine (ie moving along a line and arriving at the end of the line, moving on an adjacent line and so on), in a reproducible manner. Such displacement is ensured for example by means of 2 axes motorized perpendicular (rails 41 and 42 of Figure 1B).

According to one example, the displacement of the optical head (lighting, objective and camera) is obtained by a linear translation assembly whose movements are managed by stepping motors, which allows to scan always the same areas of the surface of collection.

It is thus possible by scanning the elementary analysis surface to obtain a few hundred acquisitions of instantaneous images, for example between 300 and 400, in order to cover a complete analysis surface of about one hundred cm. ² , equivalent to several billion pixels.

The scanning mechanism is sized according to an example to allow a complete scan in a short time, typically from a few minutes to ten minutes, which constrains the profiles of displacement.

Moreover, a sufficient rigidity of the scanning mechanism makes it possible to move the optical head while maintaining the sharpness of the image, increasing the reliability of the detection.

Examples of methods for forming images of elemental analysis surfaces from images acquired by the optical head, processing of formed images and methods of counting particles from the formed images are now described. Some or all of the methods described below may be controlled by the electronic control unit 50 (FIG. 1B) integrated in the optronic system and / or by the control computer 60 (FIG. 1A) connected to the electronic unit. control and equipped with control software.

Before performing a scan, the optronic system can alternatively test whether the ambient lighting is not too high, in order to avoid disturbing, saturating or skewing the measurements.

The formation of an image of an elemental analysis surface can be done according to the following method, illustrated by means of FIGS. 4A to 4C:

the lighting source is lit to make a first acquisition: this first acquisition determines the image of the particles by including the ambient background. Figure 4A shows the profile of an illuminated particle, that is to say the intensity of the signal from this particle, in one dimension;

the lighting source is turned off to make a second acquisition: this second acquisition determines the image of the ambient background. Figure 4B shows the profile of the same particle as Figure 4B but this time unlit;

the 2 acquisitions are subtracted pixel by pixel in order to obtain the image of the particles devoid of background. Figure 4C shows the profile of the same particle after subtraction of the two previous profiles.

The following process can then be applied to the formed image: determining a threshold level, the threshold level being a factory parameter independent of the images acquired.

a segmentation and a grouping of the contiguous pixels having a value greater than that of the previously determined threshold level are carried out. Each group of pixels thus formed constitutes a particle.

the size of a particle can be determined from the maximum distance that two of its pixels can form. A comparison of all the possible combinations between two pixels belonging to one to the upper convex envelope and the other to the lower convex envelope of the particle can be made to deduce the size of this particle.

Once the acquisitions and calculations are complete, the optical head can be translated to the next elemental analysis surface and so on.

Each particle can then be classified according to the category of its size, and for each position of the optical head. The statistics can be updated on the software interface until the end of the scan where the final particle concentration values according to the size categories can be displayed on a graph.

Using the control software implemented in the control computer, it is possible to archive the sweeps made over time and review the entire scanning campaign to analyze the images from the first to the last sweep performed. Contamination monitoring can thus be carried out by sweeping the collection surface at regular intervals and programmable by the user (for example every 5 min for almost continuous operation, or at more spaced intervals of time).

According to an exemplary embodiment, a first scan of the collection surface may be performed to characterize the initial pollution state of the surface. He is the origin of the follow-up. The subsequent scans of the collection surface can be used to follow the evolution of the contamination with respect to this first scan. One advantage is that the surface may be imperfectly clean or slightly damaged, this does not affect the monitoring of the contamination.

In parallel with each scan, a measurement of ambient noise related to the light environment can be performed. The noise value is reported in parallel with the contamination values. This makes it possible to keep in memory the light environment seen by the detection device.

The contamination results can be given for several categories, in particles / cm ² , in the form of time graphs.

FIG. 6 thus represents an example of contamination monitoring curves. surface. The curves 610, 620, 630, 640, 650 respectively represent the evolution in time of the number of particles per cm ² on the analysis surface, having sizes respectively greater than 5μιη, 15μιη, 25μιη, 50 and ΙΟΟμιη. It can be noted that on this analysis surface, the presence of particles of more than 50μιη is very low throughout the monitoring. These curves are obtained by performing several scans at regular intervals and programmable by the user; these intervals may be a few minutes, for example 10 to 15 minutes, for continuous operation, or more spaced, for example every hour. The first scan characterizes the initial pollution state of the surface and is the origin of the tracking curves. The following scans will make it possible to follow the evolution of the contamination with respect to this first scan. On these curves, there is for example a significant drop in the amount of particles per cm ² on 17/06/2014 before 15:30 (reference 611); this sudden drop corresponds to a cleaning of the analysis surface. Then over time, the amount of particles per cm ² increases, which corresponds to the accumulation of particles on the analysis surface. At time T, a scan is in progress; it is possible to follow its evolution on the display 670. The display 670 represents the analysis surface, the region 671 of the display 671 represents the region of the collection surface already scanned and the region 672 of the display 671 represents the region that has not yet been swept.

In parallel with each scan, a noise measurement can be performed. The value is reported in parallel with the contamination values. This makes it possible to keep in memory the light environment seen by the device during the measurement. Indeed, during use, there could be significant variations in background noise making the results erroneous, for example if the sensor is saturated by ambient light noise preventing any acquisition.

One of the advantages of the invention is that the surface can be perfectly clean or slightly damaged, the monitoring of the contamination will not be affected since the counting can be done relatively to an initial state as described previously; this increases the duration of use of the device.

Alarm thresholds can be set by the user when pre-defined surface contamination thresholds are reached.

According to an exemplary embodiment illustrated by means of FIGS. 7 and 8, the method according to the present description can comprise the detection of surface contamination of a controlled environment zone by means of a system of which an example is shown in FIG.

The surface contamination detection system comprises a control computer 60 equipped with control software and a set of surface contamination detection devices, as described for example by means of FIGS. 1A, 1B and 2. In the case where Single control electronics (50, Figure 1B) of each detection device controls in an integrated manner, the entire processing of images, the control computer can be used for display and interface with the user. The connection between each of the detection devices and the control computer can be done in a known manner wired or wireless.

FIG. 8 illustrates, in one example, the arrangement of surface contamination detection devices in a controlled environment zone, for example a clean room. The arrangement of the detection devices is advantageously based on the layout of the room, the sensitive elements to be protected from particulate pollution and potential sources of contamination such as for example the movements of the operators shown in Figure 8 by arrows. Thus, in the example of FIG. 8, surface contamination detection devices 101 to 112 are placed in a controlled environment zone 200 around sensitive zones ZI, Z2, Z3 which are for example at a table level. 203, shelves 202, machines 201, 204 and around the movements of the operators (represented by arrows). Each of the detection devices may be arranged to give the collection surface an inclination representative of the inclination of the sensitive surfaces of the controlled environment area. Precise modeling of contamination in time and space is possible.

Although described through a number of detailed exemplary embodiments, the systems and methods for detecting particulate contamination sedimented according to the present disclosure include various alternatives, modifications, and improvements that will be apparent to those skilled in the art, it being understood that these various variants, modifications and improvements fall within the scope of the invention, as defined by the following claims.

Claims

A method for detecting surface contamination by particles evolving in free air in a zone to be monitored (200), comprising:

arranging in the area to be controlled at least one fixed collecting surface (10) receiving particles on one of its faces (11);

for each collection surface (10), illuminating a region of said collection surface by means of a light beam emitted from a light source (34, 35) located in an optical head (30) said optical head being disposed on the side of the collecting surface opposite the particle receiving face (11);

forming an image of an elemental analysis surface (13i) of the illuminated region by means of an imaging optical system (38) arranged in the optical head (30), each particle sedimented on the analysis surface elementary (13i) emitting a backscattered light signal;

moving the optical head (30) to scan in both directions of the collection surface and at each scan point an image of the elemental analysis surface;

A method of detecting surface contamination according to claim 1, wherein the illumination beam is oriented such that the beam resulting from the specular reflection of the illumination beam on the collection surface (10) does not penetrate the imaging optical system (38).

A method of detecting surface contamination according to claim 1, wherein the displacement of the optical head is such as to form juxtaposed and disjoint elemental analysis surfaces (13i) covering the entire collection surface (10). ).

A method of detecting surface contamination according to any one of the preceding claims comprising, for each image formation of an elemental analysis surface, acquiring a first image of the elemental analysis surface by means of of the imaging optical system with lighting, the acquisition of a second image of the elemental analysis surface by means of the imaging optical system without illumination, the subtraction of the two images to form the image of the elemental analysis surface.

A method for detecting surface contamination according to any one of the preceding claims comprising, for each image formed of an elemental analysis surface, the estimation of a threshold level and the detection of the points of the image presenting a higher than the threshold level for particle detection and size determination.

A method of detecting surface contamination according to any one of the preceding claims, further comprising the temporal tracking of the detected particles.

A method of detecting surface contamination according to claim 6 comprising a first scan of the collection surface performed to characterize the state of initial pollution of the surface, causing the time tracking.

A method of detecting surface contamination of a controlled environmental area comprising detecting surface contamination as claimed in any one of the preceding claims at different locations in the area.

A surface contamination detecting device (100) comprising:

a fixed collection surface (10) intended to receive particles evolving in free air on one of its faces (11);

an optical head (30) arranged on the side of the collection surface opposite the particle receiving face (11) and comprising:

an imaging optical system (38) for forming an image of an elemental analysis surface (13i) of the collection surface (10) on a detection surface (33);

a light source (34, 35) for emitting at least one lighting beam adapted to cover said elemental analysis surface

(130;

moving means (40) of the optical head (30) for scanning in both directions of the collecting surface (10) and at each point of the scanning, forming an image of the elemental analysis surface; an electronic control unit (50) for processing the signals from the imaging optical system.

The surface contamination detecting device (100) according to claim 9, wherein the illumination beam is oriented such that the beam resulting from the specular reflection of the illumination beam on the collection surface (10) does not does not enter the imaging optical system (38).

11. Surface contamination detection device (100) according to one of claims 9 or 10, wherein the illumination source comprises at least two elementary sources (34, 35) arranged on either side of the optical imaging system. and whose emission covers said elementary surface (13i).

The surface contamination detecting device (100) according to one of claims 9 to 11, wherein the imaging optical system (38) comprises a lens (31) and a two-dimensional detector (32) having a detection surface (33). ) whose dimensions define the dimensions of the elemental analysis surface (13i).

13. Surface contamination detection device (100) according to one of claims 9 to 12, wherein the imaging optical system (38) comprises a spectral filter (36) adapted to transmit only the emission spectral band of the lighting source.

A surface environmental contamination detection system of a controlled environmental area comprising a set of surface contamination detecting devices (101 - 112) according to any one of claims 9 to 13 and a control unit (60) of the devices. .