WO2014158013A1

WO2014158013A1 - Airborne particles deposition detection

Info

Publication number: WO2014158013A1
Application number: PCT/NL2013/050221
Authority: WO
Inventors: Antonius Wessel VAN DENZEL; Niels Willem-Jan Kolthoff; Jan GERBRANDS
Original assignee: Technology Of Sense B.V.
Priority date: 2013-03-26
Filing date: 2013-03-26
Publication date: 2014-10-02

Abstract

The invention relates to airborne particles deposition detection. An airborne particles deposition detection system comprising: a particles deposition accumulating disposable with a body portion forming a particles accumulation surface on which in use depositing particles from the air accumulate; and, a particles deposition sensor station to detect particles deposition on the disposable. The sensor station comprises: a holder adapted to releasable hold the disposable; a radiation device adapted to radiate a radiation beam to the disposable; and, a radiation detector adapted to receive the radiation beam. The radiation detector receives an interference pattern caused by interference between an unscattered portion of the radiation beam and the radiation beam being scattered from a calibration mark and /or a particle deposited on the particles accumulation surface to detect any deposited airborne particles.

Description

AIRBORNE PARTICLES DEPOSITION DETECTION The invention relates to an airborne particles deposition detection system to detect airborne particles deposition on a particles deposition accumulating disposable. Such system may be useful to detect particles that fall out from the air in an air quality controlled room, such as a cleanroom, e.g. in the electronics, high-tech manufacturing, aircraft, space, or food industry, or e.g. in a medical surgery room. The particles deposited on the disposable may be detected to make a determination of the fall out of airborne particles possible and to monitor the air quality.

GB1326343 discloses an airborne particles deposition detection system including a plate, which is exposed to the air to be monitored to allow fall out particles to accumulate on its surface. After a monitoring period the plate is inserted in a detection apparatus of the system to detect accumulated particles on the surface. Within the apparatus a light source is directed to the plate and particles on the plate are detected with a light measuring device. A calibration device is provided within the apparatus to calibrate its sensitivity to particles. The working of this known system is however unsatisfactory.

Its an objective of the invention to provide an improved airborne particles deposition detection system. Accordingly there is provided an airborne particles deposition detection system according to claim 1.

The system allows for a satisfactory detection of airborne particles that are accumulated on the accumulation surface of the disposable as the one or more calibration marks that seen by the detector together with the deposited particles allow for an efficient and reliable interpretation of the interference pattern of the particles. In a simplest form output image data representing the interference pattern of the deposited particles is directly displayed as an image on a display, so as to allow for visual human interpretation of the image by a control person. The one or more calibration marks than provide information that serves as calibration when identifying e.g. the size and/or number of deposited particles.

In a preferred embodiment, the system is provided with a detector output device to output image data representing the interference pattern received on the radiation detector, the detector output device being operably connectable or connected, e.g. wireless, with a computer of the system, preferably a computer arranged in a stand alone unit remote from the sensor station. The computer comprises a processor connected to a memory and the memory is provided with software which when run on the processor performs calculations with the image data from the radiation detector to calculate at least one of:

- an indication of the number of particles accumulated on the accumulation surface of the disposable;

- an indication of the size of the particles accumulated on the accumulation surface of the disposable; and,

- an alarm activation signal if the indication of the number or size of the particles accumulated on the accumulation surface of the disposable is outside an allowable range or value.

An advantage of a remote arrangement of the computer that performs said calculations, preferably outside the cleanroom, is that heat from the computer does not affect the air near the sensor station which might occur if the computer is integrated into the sensor station.

The alarm activation signal may be used to active an alarm mechanism that is optionally provided for in the sensor station, e.g. a visual and/or audible alarm. The alarm may e.g. indicate a local source of contamination, e.g. a person having contaminated clothing or an object or tool being brought into the cleanroom that is contaminated and releases particles. Subsequent to an alarm measures such as cleaning or inspecting the cleanroom to see what caused the particle contamination may be taken. The stand-alone unit may include a display on which said one or more indications are displayed. The occurrence of alarm activation may also be displayed. The system, e.g. the stand-alone unit, may also include a memory wherein said image data and/or indications are logged, e.g. in view of later review and/or use thereof for performing calculations on the basis of new image data in combination with older image data from the sensor station.

In an embodiment the sensor station is portable, allowing to place the sensor station at a suitable location in the room, e.g. at a workplace where one or more person perform activities in a cleanroom. If work has to be done at another location in the cleanroom, or in another cleanroom, the sensor station can be moved to said other location.

In an embodiment multiple sensor stations are provided in combination with a single computer in a stand-alone unit. According to an embodiment a radiation transmissive body portion of the disposable is provided with the one or more calibration marks, possibly - as is preferred - all calibration marks seen by the radiation beam are provided on the disposable. By providing the calibration marks on the disposable, the interpretation of the image data is enhanced, e.g. as small displacements of the disposable relative to the sensor station, e.g., whilst being held in the holder, do not affect the position of the calibration marks relative to the accumulation surface.

Also each time a disposable is replaced for a new clean disposable, the calibration marks are also renewed so that detonation of the calibration over time does not occur.

The provision of the calibration marks on the disposable instead of on a component of the sensor station also allows to use disposables with differently embodied accumulation surfaces in combination with the sensor unit, e.g. for different applications.

Preferably the system, e.g. the software, is embodied to recognize the disposable, e.g. based on the calibration marks thereon and/or a unique code assigned to the disposable

Preferably the one or more calibration marks are arranged on the disposable so as to be - in direction of the traversing radiation beam - aligned with the accumulation surface or the one or more calibration marks are actually arranged on the accumulation surface. This means that the calibration marks are imaged by the radiation beam within the image of the deposited particles. In another approach the calibration marks are arranged on a portion of the disposable that is not aligned with the accumulation surface in direction of the radiation beam, yet also traversed by the radiation beam at the same time, so that the calibration marks appear in one or more regions of the image that are distinct from the region that images the interference pattern of the deposited particles.

In an embodiment a plurality of calibration marks is located in a common plane, e.g. in a plane that is parallel to or coincides with the accumulation surface of the disposable or a sub-surface thereof. As will be explained in more detail below the accumulation surface can, and preferably is, be composed of multiple sub-surfaces arranged in series behind one another in the direction of the beam so as to allow for an increase of the accumulation surface.

The plurality of calibration marks may be used, e.g. by the software run on the processor, as references to allow for the determination of for example the dimension of detected particles and/or distances between detected particles and/or locations of detected particles on the accumulation surface of the disposable.

The plurality of marks may also be used, e.g. by software run on the processor, to determine whether the disposable is correctly positioned in the holder, e.g. to detect that the disposable is undesirably tilted, arranged in reversed position, etc. The system may be embodied to provide an alarm if an incorrect position of the disposable in the sensor station is detected. In an embodiment a plurality of calibration marks is provided having a size between

1 and 1000 micrometers, preferably between 5 and 500 micrometers, more preferably between 10 and 250 micrometers.

In an embodiment a plurality of calibration marks is provided comprising at least a first group of first calibration marks, preferably located in a common plane, said first calibration marks each having a first size, e.g. between 5 and 20 micrometers.

By having multiple calibration marks of a given first size, notably a very small size as above, it becomes effective to interpret the image data in order to determine the size of deposited particles.

Possibly, and advantageously, a second group of second calibration marks is provided each having a second size larger than the first size, e.g. between 25 and 70 micrometers. Preferably said first and second groups of calibration marks are located in a common plane. By providing calibration marks with a different second size it becomes possible to calibrate the size of detected particles more accurate. It also becomes possible to differentiate between calibration marks using the size as an identifier.

In a further development even a third group of third calibration marks is provided, each having a third size larger than the first size and than the second size, e.g. between 75 and 250 micrometers. Preferably this third group of calibration marks is located in a common plane with said first and second groups of calibration marks. By providing calibration marks with a first, a second, and a third size it becomes possible to calibrate the size of particles even more accurate and identify even more calibration marks. According to a further embodiment at least one of the first, second, and third group of calibration marks comprises three calibration marks positioned in a common plane and along a straight line. The later may be useful to determine the deviation and accuracy of the calibration marks inside the common plane.

In an embodiment at least one of the first, second, and third group of calibration marks comprises four calibration marks arranged in a common plane and each positioned on a corner of an imaginary quadrangle. The quadrangle may be a square or a rhombus. The quadrangle may be used to define a quadrangle on a common plane with a certain size, which may be used to calibrate for example a particles deposition accumulating surface.

In an embodiment in at least one of the first, second, and third group of calibration marks, some of the calibration marks are positioned in pairs of two that are closer to one another than to other calibration marks of said group. In this way a distance and a direction as well as a position may be calibrated.

In an embodiment the disposable has a plane that is provided with multiple calibration marks and which plane is divided in two imaginary halves by an imaginary axis, and wherein the calibration marks in said two imaginary halves are not symmetrical relative to said axis. With the marks positioned asymmetrical it becomes possible to calibrate which end of the disposable is where relative to the direction of travel of the radiation beam, e.g.

allowing to detect whether the disposable is placed in reverse in the holder when such is of interest.

In an embodiment calibration marks with a relatively smaller size are provided close to a centre of a common plane e.g. closer to a centreline of the radiation beam and calibration marks with a relatively larger size are provided further away from said centre(line). The angle of diffraction of the radiation by the smaller calibration marks is larger than the angle of diffraction of larger calibration marks. By providing the smaller calibration marks in or near the centre although the angle may be larger there may still be sufficient energy received on the radiation detector. If one would position the smaller marks further away from the centre a portion of the diffracted energy may pass the radiation detector away from an effective detecting surface of the radiation detector. The larger calibration marks may be provided further away from the centre because the angle of diffraction is smaller such that sufficient energy will be received at the detecting surface of the radiation detector.

Advantageously, a common plane in which multiple calibration marks are provided may be the particles accumulation surface. By having the particles accumulating on the same surface as where the calibration marks are provided the distance between the marks and the particles is kept small increasing the accuracy of the system. Alternatively, the common plane in which the marks are provided is on a different surface than the surface on which the particles are accumulating, e.g. on a side of a uniform thickness wall portion which forms the accumulation surface.

In an embodiment the plurality of calibration marks comprise calibration marks with different shapes. In this way it e.g. becomes possible to recognize different calibration marks. Which may be helpful to identify the calibration mark and/ or the disposable with the system.

In a preferred embodiment at least the body portion of the disposable forming the particles accumulation surface and the body portion of the disposable that is provided with the one or more, preferably all, calibration marks are injection moulded of plastic material as a unitary plastic body. More preferably the entire disposable with all its marks is injection moulded as a unitary plastic body. For example, each calibration mark is embodied as an integrally moulded protrusion.

It will be appreciated that the one or more marks may also be made on a plastic disposable by another technique, e.g. by laser engraving, by drilling, by etching, etc.

In a preferred embodiment the particles accumulation surface of the disposable is formed by multiple particles accumulation sub-surfaces, said sub-surfaces being positioned behind each other in a first direction substantially parallel to the radiation beam. This allows to increase the effective accumulation surface that is imaged onto the detector by the radiation beam, as the beam passes through all said sub-surfaces.

In an embodiment one or more of the calibration marks are provided on or adjacent a leading sub-surface and one or more calibration marks on or adjacent a second sub-surface of the multiple sub-surfaces. One or more calibration marks may be provided on or adjacent a last sub-surface of the multiple sub-surfaces positioned behind each other in the first direction of the beam. In this way by detecting the calibration marks it becomes possible to detect a position of the disposable with a high accuracy. It also becomes very effective to determine the size and/or the position of deposited particles on the sub-surfaces.

According to a further embodiment a leading sub-surface may receive the radiation beam of the radiation device first and a last sub-surface may receive the radiation beam last from all the sub-surfaces and calibration marks on or adjacent the leading sub-surface may be positioned closer to a centre of the first particles accumulation sub-surface than the calibration marks on or adjacent the last sub-surface.

The last sub-surface preferably is closer to the radiation detector while the leading sub-surface is further away from the radiation detector. If the diffraction angle is taken constant (for example by taking a mark with the same size) the spread of the diffracted energy at the detecting surface of the radiation detector is larger if the diffraction occurs further away from the radiation detector (for example at the leading sub-surface). By providing the calibration marks more at the centre of the radiation beam although the spread may be larger the detecting surface of the radiation detector still receives sufficient diffracted energy to use the calibration mark.

According to a further embodiment the leading sub-surface receives the radiation beam first and the last sub-surface receives the radiation beam last from all the sub-surfaces and the calibration marks on or adjacent the leading sub-surface are relatively larger than the calibration marks on or adjacent the last sub-surface. The last sub-surface may be closer to the radiation detector while the leading sub-surface is further away from the radiation detector. By having larger calibration marks (with consequently smaller diffraction angels) on the leading sub-surface more of the diffracted energy may reach the detecting surface of the radiation detector than if smaller calibration marks were used (with consequently larger diffraction angels). Closer to the radiation detector smaller calibration marks may be used because although the diffraction angle is larger the relatively short distance to the radiation detector still assures that enough of the diffracted energy will reach the detecting surface of the radiation detector. Advantageously, the radiation detector may be positioned as close as possible to the calibration marks and or the accumulating surface to increase the sensitivity of the system.

According to an embodiment the leading sub-surface receives the radiation beam first and the last sub-surface receives the radiation beam last from all the sub-surfaces and the calibration marks on or adjacent the leading sub-surface are different of size and differently positioned than the calibration marks on or adjacent the last sub-surface. The diffraction angle and the position with respect to the radiation detector may be taken into account to optimize the amount of diffracted energy received by the radiation detector. According to an embodiment the sub-surfaces of the disposable are tilted with respect to the first direction of the radiation beam between 10 to 80°, preferably between 30 to 60° and most preferable between 40 to 50°.

According to an embodiment the sub-surfaces of the disposable are in zig-zag formation relative to the beam when seen in side view, e.g. in a V-arrangement of an adjoining sub-surfaces, e.g. with multiple V-formations of sub-surfaces in series. For example the disposable has two groups of particles accumulation sub-surfaces, a first group of sub-surfaces tilted with respect to the first direction between 10 to 80°, preferably between 30 to 60° and most preferable between 40 to 50° and a second group of subsurfaces tilted with respect to the first direction between -10 to -80°, preferably between -30 to -60° and most preferable between -40 to -50°. The sub-surfaces of the first and second group of sub-surfaces are positioned alternating one behind the other in the first direction.

Preferably the body portion forming the accumulation surface is a solid, non-porous body portion, thus not a filter body, as any pores or small channels therein may result in scattering of the radiation beam which impairs the effectiveness of the system.

Preferably the body portion forming accumulation surface is composed of subsurfaces, which form a smooth, planar and closed, non-porous accumulation surface. According to an embodiment the radiation detector is connected to a primary transmitter within the sensor station to transmit primary data from the particles deposition sensor station; and the system further is provided with a stand alone unit positioned away from the sensor station and provided with a primary receiver to receive primary data transmitted from the sensor station. By providing the stand alone unit away from the sensor station there is no need to have the heat (and consequently air turbulence) producing computer in the cleanroom that may influence the accuracy of the particle detection system and/or any other apparatus present in the clean room.

The stand alone unit may comprise a secondary transmitter and the sensor station may comprises a secondary receiver to receive secondary data transmitted from the stand alone unit to the particles deposition sensor station. The sensor station may be provided with an alarm connected to the secondary receiver and the stand alone unit may be constructed and arranged to transmit secondary data comprising an alarm activation signal via the secondary transmitter to the secondary receiver of the sensor station to activate the alarm.

According to an embodiment the sensor station may be provided with a battery holder for holding a rechargeable battery to provide electricity to the sensor station. The stand alone unit may be provided with a battery charger for charging said battery. By providing a battery to the sensor station no separate energy connector may be necessary for the sensor station.

According to a further embodiment the stand alone unit is provided with a computer connected to the primary receiver to receive and process image data from the radiation detector of the sensor station. The computer may comprise a processor connected to a memory and the memory is provided with software which when run on the processor performs calculations on the image data from the radiation detector, e.g. to provide an indication for the number of particles accumulated on the accumulation surface of the disposable, an indication of the size of particles accumulated on the accumulation surface of the disposable, and/or an indication of the size and/or position of one or more calibration marks, preferably provided on the disposable.

According to an embodiment the processor may be connected to a system output to transmit an output signal which output signal is the result of image data processed by the processor.

In a preferred embodiment the sensor station comprises a housing having one or more housing parts, preferably a single housing. The radiation device and the radiation detector are arranged within said housing. The holder is adapted to releasable hold the disposable externally of the housing, most preferably such that the accumulation surface faces upwards so as to receive thereon depositing particles while being held stationary by the holder relative to the housing. At least one window is provided in the housing to provide the radiation beam from the radiation device to the accumulation surface and further to the radiation detector to detect any deposition particles on the accumulation surface of the disposable. Preferably two windows are arranged spaced apart from one another, with the holder being adapted to hold the disposable between the windows, preferably holding said disposable in stationary position there between. Preferably each window, which could be a simple opening in the housing, is provided with a radiation transmissive window pane so that particles are not entering the housing and may not soil the radiation device and/or detector.

Preferably, in particular with a monochromatic radiation beam, e.g. a laser beam, each window pane is embodied as a radiation band pass filter to block any radiation different than the radiation beam from entering the housing or housing parts. Radiation from other sources in the environment of the sensor station, e.g. lighting equipment, may disturb the radiation detector. By providing a band pass filter those other sources are be filtered out.

The holder may be constructed to hold the disposable stationary in the holder. If the disposable moves in the holder during a measurement cycle the measurement may be disturbed. The holder may comprise a void or recess provided on the outside of the housing to hold the disposable therein. According to an embodiment the radiation device is adapted to produce a radiation beam with substantially monochromatic radiation which may be optical radiation, e.g. a laser device. Monochromatic radiation will give the optimal interference patterns on the radiation detector.

According to an embodiment the disposable when placed in the holder is covering the one or more windows and/or window panes of the sensor station. In this way the window(s) will be protected for depositing particles by the disposable. According to an embodiment the window is an open window. If the disposable is at least partially covering the open window the interior of the housing will be protected for depositing particles by the disposable.

According to an embodiment the window has a first window to provide the radiation beam from the radiation device inside the housing to the disposable outside the housing and a second window to provide the radiation beam from the particles deposition accumulation disposable outside the housing to the radiation detector inside the housing.

The radiation detector may comprise a CCD camera, which is simple and effective means for capturing the image data from the received radiation beam and interference pattern of the deposited particles and of the one or more calibration marks.

According to an embodiment the radiation device is a pulsed radiation device adapted to radiate a pulsed radiation beam and the radiation detector is adapted to take pictures with image data of the interference pattern created with the pulsed radiation beam, e.g. one picture per pulse.

The system may be adapted to emit the radiation beam that traverses through the accumulation surface and to collect and preferably also process image data from the detector according a timing sequence, e.g. in a periodic manner, preferably an adjustable timing sequence. For example the system is adapted to allow an operator to set a time interval, for example an adjustable interval of e.g. 1 , 5, 10, 15, 30, or 60 minutes, with the system radiating the accumulation surface, collecting and processing the image data at the end of each interval.

For example the disposable is kept in the holder of a sensor station until the accumulation of particles thereon has reached a predetermined exchange level, whereat the disposable needs to be exchanged for a new disposable. For example the system provides a signal indicating the requirement to change a soiled disposable for a new disposable. During the service life of the disposable, which will then primarily depend on the actual contamination by the fall out particles, the system will repeatedly operate the sensor station to obtain image data from the detector and preferably perform the mentioned calculations based on those image data.

For example the disposable is kept in the holder of the sensor stations for one or more hours, e.g. a work shift in a cleanroom, or e.g. for a work day, and the system will repeatedly operate the sensor station during said service life period of the disposable.

In a system with a computer, a software controlled operating method thereof may comprise:

- storing in a memory of the computer an indication of a number of particles calculated at a first moment in time;

- calculating with image data received from the detector at a second, later moment in time a new indication of a number of particles accumulated on the accumulation surface of the same disposable; and,

- deriving from the new indication of the number of particles accumulated on the accumulation surface of the disposable and the stored indication a rate of particles deposition

corresponding to the time interval between the first and the second moments.

The radiation device and the radiation detector may controlled so as to be switched off when their operation is not required so as to safe energy and not to dissipate any heat which may effect airflow in the vicinity of the sensor station.

According to an embodiment the disposable may comprise an identification code, e.g. a unique code for each disposable or a code representing a batch of disposables, with the sensor station being equipped with a reader device adapted to automatically read the code when the disposable is arranged in the holder. For example the code is a barcode, e.g. a 2D- barcode, and the reader is an optical barcode reader.

Preferably the disposable is provided with an RFID chip providing a code for identification of the disposable and the sensor station is equipped with an RF receiver to read the code of the RFID chip. Preferably the RFID chip is embedded in an injection moulded plastic disposable so that the chip is an integral part of the disposable.

Preferably the identification code is transmitted along with the image data to the computer. The system may be adapted to store the identification code along with the calculation results obtained from the use of the particular disposable for logging purposes. The system may be adapted to use the identification in order to facilitate the identification and/or locating of calibration marks on the disposable, e.g. by creating a reference to a pre- stored reference image of the calibration marks.

The identification code, and the first time recognition thereof by the sensor station when a new disposable is placed in the holder, may also be employed to trigger a calibration routine of the computer and/or the sensor station. It may also be used later on with a track and trace system possible to trace a used disposable.

According to a further embodiment there is provided a disposable constructed for cooperation with a sensor station of the system as described herein.

According to a further embodiment there is provided a sensor station constructed for cooperation with a disposable of the particles deposition system as described herein.

According to the invention there is also provided a method for detecting airborne particles deposition, the method preferably using a system as disclosed herein, the method comprising:

releasable holding a particles deposition accumulating disposable with a body portion of radiation transmissive material that forms a particles accumulation surface in order to accumulate depositing particles on said accumulation surface,

providing a radiation beam from a radiation device of a sensor station to the disposable so as to traverse said body portion of radiation transmissive material that forms the accumulation surface;

detecting with a radiation detector of the sensor station the radiation beam traversed through the accumulation surface of the disposable by receiving the radiation beam on the radiation detector;

receiving an interference pattern caused by interference between an unscattered portion of the radiation beam and a portion of the radiation beam being scattered from:

- one or more calibration marks provided on at least one of a radiation transmissive body portion of the disposable and, if present, a radiation transmissive component of the sensor station through which said radiation beam traverses; and,

-particles deposited on the accumulation surface of the disposable;

and,

processing the interference pattern in a computer to calibrate the disposable and/or the sensor station and to detect any depositing particles on the accumulation surface.

According to an embodiment the method further comprises calibrating the size of a depositing particle by creating an interference pattern on the radiation detector by interference of a portion of the radiation beam being scattered by the one or more calibration marks and an unscattered portion of the radiation beam.

According to an embodiment the method further comprises removing the disposable from the holder after repeated steps of radiating the accumulation surface thereof with the disposable in said holder (preferably stationary), collecting and processing the image data thus obtained from the holder of the sensor station, and replacing the removed disposable with a new disposable. The other disposable being a clean one with substantially no particles accumulated on it.

Preferably each disposable is packaged in a sealed packaging prior to its use, e.g. in a bag or envelope.

According to an embodiment the method comprises calculating with image data from the radiation detector an indication of a number of particles accumulated on the accumulation surface of the disposable. In this way the airborne particles deposition may be determined.

According to an embodiment the method comprises:

- storing in a memory an indication of a number of particles calculated at a first moment; - calculating with image data obtained at a second, later moment from the radiation detector a new indication of a number of particles accumulated on the disposable; and,

- deriving from the new indication of the number of particles accumulated on the disposable and the stored indication, a rate of particles deposition corresponding to the time interval between the first and the second moments.

According to an embodiment the method comprises comparing the rate of particles deposition with a range or value for an acceptable rate of particles deposition and activating an alarm if the rate of particles deposition is higher than the acceptable range or value. According to an embodiment the method comprises calculating with image data from the radiation detector an indication of the size of particles accumulated on the disposable.

According to an embodiment the method comprises transmitting an output signal comprising an indication of a number of particles accumulated on the particle accumulating disposable or an indication of the size of particles accumulated on the disposable.

According to an embodiment the method comprises transmitting primary data of the radiation detector from the sensor station with a primary transmitter and receiving the primary data with a primary receiver provided to a stand alone unit positioned away from the particles deposition sensor station.

According to an embodiment the method comprises transmitting image data representing an interference pattern received at the radiation detector as the primary data.

According to an embodiment the method comprises positioning at least one sensor station in a cleanroom and positioning the stand alone unit outside the cleanroom. The stand alone unit will in this way not occupy any valuable cleanroom space and it will not heat up the cleanroom causing disadvantageous air turbulence.

The method may comprise calculating at the stand alone unit with the image data from the radiation detector a number of particles accumulated on the disposable. The method may comprise transmitting secondary data with a secondary transmitter provided to the stand alone unit to a secondary receiver provided to the particles deposition sensor station.

The method may comprise transmitting an alarm activation signal as secondary data via the secondary transmitter to the secondary receiver of the sensor station activating an alarm.

The invention further relates to a particles deposition accumulating disposable comprising a body portion forming an accumulation surface to accumulate depositing particles thereon and being transmissive for a radiation beam, wherein at least one calibration mark is being provided to the transmissive body portion of the disposable.

The calibration mark may assure a fast calibration of a system employing the disposable.

The accumulation surface of the disposable may be composed of multiple subsurfaces each to accumulate depositing particles thereon and the multiple sub-surfaces are positioned behind each other in a first direction.

A first calibration mark may be provided on or adjacent a first sub-surface and a second calibration mark may be provided on or adjacent another sub-surface of the multiple sub-surfaces positioned behind each other in the first direction.

The second calibration mark may be provided on a last sub-surface of the multiple sub-surfaces of the multiple sub-surfaces positioned behind each other in the first direction.

The sub-surfaces of the disposable may be tilted with respect to the first direction between 10 to 80°, preferably between 30 to 60° and most preferable between 40 to 50°. The sub-surface of the disposable may be divided over two groups of sub-surfaces, a first group of sub-surfaces tilted with respect to the first direction between 10 to 80°, preferably between 30 to 60° and most preferable between 40 to 50° and a second group of sub-surfaces tilted with respect to the first direction between -10 to -80°, preferably between - 30 to -60° and most preferable between -40 to -50°. The first and second group of subsurface are positioned alternatingly behind each other in the first direction.

The disposable may comprise a RFID chip for identification of the disposable to a RF receiver provided in the sensor station. The invention also pertains to embodiments that are disclosed in the following numbered clauses:

1. An airborne particles deposition detection system to detect particles deposition from the air and provided with a particles deposition detection assembly comprising:

- a particles deposition accumulating disposable with a body portion of radiation transmissive material, the body portion forming a particles accumulation surface on which in use depositing particles from the air accumulate; and,

- a particles deposition sensor station to detect particles deposition on the particles accumulation surface.

2. The system according to clause 1 , the sensor station comprising:

- a holder adapted to releasable hold the disposable;

- a radiation device adapted to emit a radiation beam to the disposable; and,

- a radiation detector adapted to receive the radiation beam; the holder of the sensor station being adapted to releasable hold the disposable with its body portion forming the particles accumulation surface in the radiation beam traversing from the radiation device to the radiation detector, the radiation detector receiving an interference pattern caused by interference between an unscattered portion of the radiation beam and a portion of the radiation beam being scattered from:

- one or more calibration marks provided on at least one of a radiation transmissive body portion of the disposable and, if present, a radiation transmissive component of the sensor station through which said radiation traverses, allowing to calibrate the system; and,

- any particles deposited on the particles accumulation surface of the disposable, allowing to detect said deposited particles,

wherein, preferably, a plane is provided with a plurality of calibration marks and the plane is a common plane for the plurality of calibration marks.

3. The system according to clause 2, wherein the plurality of calibration marks comprise a first group of first calibration marks with a first size. 4. The system according to clause 4, wherein the plurality of calibration marks further comprises a second group of second calibration marks, preferably in a common plane, each second calibration mark having a second size larger than the first size.

5. The system according to clause 4, wherein the plurality of calibration marks further comprises a third group of third calibration marks, preferably in said common plane, each third calibration mark having a third size larger than the first size and than second size.

6. The system according to clause 3, 4 or 5, wherein at least one of the first, second, and third group of calibration marks comprises three calibration marks, in a common plane and positioned along a straight line.

7. The system according to clause 3, 4 or 5, wherein at least one of the first, second, and third group of calibration marks comprises four calibration marks, in a common plane each positioned on a corner of a quadrangle.

8. The system according to clause 3, 4 or 5, wherein at least one of the first, second, and third group of calibration marks are positioned in pairs of two.

9. The system according to any of clauses 3 to 8, wherein a plane is divided in two imaginary halves by an axis and one of the groups calibration marks is positioned in one of the two imaginary halves.

10. The system according to any of clauses 2 to 9, wherein calibration marks with a relatively smaller size are provided close to a centre of a common plane or of the centreline of the radiation beam and calibration marks with a relatively larger size are provided further away from the centre or the centreline of the radiation beam.

11. The system according to any of clauses 2 to 10, wherein a plane with multiple calibration marks is parallel to or coincides with the particles accumulation surface or a subsurface thereof.

12. The system according to any of the preceding clauses, wherein the disposable is provided with a plurality of calibration marks and the plurality of calibration marks comprise calibration marks with different shapes or sizes.

13. The system according to any of the preceding clauses, wherein the particles accumulation surface of the disposable is formed by multiple particles accumulation sub- surfaces, and said sub-surfaces are positioned behind each other in a first direction that is in operation preferably substantially parallel to the radiation beam.

14. The system according to clause 13, wherein a first calibration mark or group of calibration marks is provided on a leading sub-surface and a second calibration mark or group of calibration marks is provided on a second sub-surface.

15. The system according to clause 14, wherein the second calibration mark or group of calibration marks is provided on a last sub-surface of the disposable as seen in the first direction. 16. The system according to clause 15, wherein the leading sub-surface receives the radiation beam first and the last sub-surface receives the radiation beam last from all the subsurfaces, and wherein the calibration marks on the leading sub-surface are positioned closer to a centre of the leading sub-surface than the calibration marks on the last sub-surface, which are positioned further away from a centre of the last sub-surface.

17. The system according to clause 15 or 16, wherein the leading sub-surface receives the radiation beam first and the last sub-surface receives the radiation beam last from all the sub-surfaces and the calibration marks on the leading sub-surface are relatively larger than the calibration marks on the last sub-surface.

18. The system according to clause 15, wherein the leading sub-surface receives the radiation beam first and the last sub-surface receives the radiation beam last from all the subsurfaces and the majority of the calibration marks on the leading sub-surface are different of size and differently positioned than the majority of the calibration marks on the last subsurface.

19. The system according to any of clauses 13 to 18, wherein the particles accumulation sub-surface of the disposable are tilted with respect to the first direction between 10 to 80°, preferably between 30 to 60° and most preferable between 40 to 50°.

20. The system according to any of clauses 13 to 19, wherein the sub-surfaces of the disposable are arranged in a V to connect two sub-surfaces in one direction, and the sub- surfaces comprise a first group of sub-surfaces tilted with respect to the first direction between 10 to 80°, preferably between 30 to 60° and most preferable between 40 to 50° and a second group of sub-surfaces tilted with respect to the first direction between -10 to -80°, preferably between -30 to -60° and most preferable between -40 to -50°.

21. The system according to any of the preceding clauses, wherein the system is provided with a detector output device to output image data representing the interference pattern received on the radiation detector, the detector output device being operably connectable with a computer comprising a processor connected to a memory and the memory is provided with software which when run on the processor performs calculations with the image data from the radiation detector to calculate at least one of:

- an alarm activation signal if the indication of the number or size of the particles accumulated on the surface of the disposable is outside an allowable range or value.

22. The system according to any of the preceding clauses wherein: the radiation detector is connected to a primary transmitter to transmit primary image data from the sensor station; and,

a stand alone unit positioned away from the sensor station and provided with a primary receiver to receive primary image data transmitted from the sensor station.

23. The system according to clause 22, wherein the stand alone unit comprises a secondary transmitter and the sensor station comprises a secondary receiver to receive secondary data transmitted from the stand alone unit to the particles deposition sensor station, e.g. wherein the sensor station provided with an alarm connected to the secondary receiver and the stand alone unit is constructed and arranged to transmit secondary data comprising an alarm activation signal via the secondary transmitter to the secondary receiver of the sensor station to activate the alarm.

24. The system according to any of clauses 1 to 23, wherein the sensor station is provided with a battery holder for holding a rechargeable battery to provide electricity to the sensor station and the stand alone unit is provided with a battery charger for charging said rechargeable battery.

25. The system according to any of clauses 21 to 24, wherein the stand alone unit is provided with a computer connected to the primary receiver to receive and process data from the radiation detector of the particles deposition sensor station.

26. The system according to clause 25, wherein the computer comprises a processor connected to a memory and the memory is provided with software which when run on the processor performs calculations with the data from the radiation detector to provide:

- an indication of the number of particles accumulated on the disposable;

- an indication of the size of particles accumulated on the disposable; and,

- an indication of the size and or position of a calibration mark provided to the disposable.

27. The air particle detection system according to any clauses 25 to 26, wherein the processor is connected to a system output to transmit an output signal which output signal is the result of image data processed by the processor.

28. The system according to any of clauses 1 to 27, wherein the sensor station comprises a housing and the holder is adapted to releasable hold the disposable externally of the housing and at least one window being provided in the housing to provide the radiation beam from the radiation device to and through the accumulation surface and then to the radiation detector to detect any deposited particles on the accumulating surface of the disposable.

29. The system according to any of clauses 1 to 28, wherein the holder is constructed to hold the disposable stationary in the holder. 30. The system according to any of clauses 1 to 29, wherein the holder may form a recess on the outside of the housing to hold the disposable.

31. The system according to any of clauses 1 to 30, wherein the radiation device is adapted to provide a radiation beam with substantially monochromatic radiation.

32. The system according to any of clauses 28 to 31 , wherein the disposable is covering the window, when placed in the holder.

33. The system according to any of the preceding clauses wherein the window is provided with a radiation transmissive material.

34. The system according to clause 33, wherein the radiation transmissive material is provided with an optical radiation band pass filter to block any radiation different than the radiation of the radiation device.

35. The system according to any of clauses 28 to 34, wherein the window is an open window.

36. The system according to any of clauses 28 to 35, wherein the window has a first window to provide the radiation beam from the radiation device inside the housing to the disposable outside the housing, and a second window to provide the radiation beam from the disposable outside the housing to the radiation detector inside the housing.

37. The system according to any of clauses 1 to 36, wherein the radiation detector comprises a CCD camera.

38. The system according to any of clauses 1 to 37, wherein the radiation device is a pulsed radiation device adapted to radiate a pulsed radiation beam and the radiation detector is adapted to take one or more pictures of the interference pattern created with the pulsed radiation beam.

39. The system according to any of clauses 1 to 38, wherein the disposable comprises a RFID chip comprising code for identification of the disposable to a RF receiver provided in the sensor station.

40. A particles deposition accumulating disposable constructed for cooperation with a sensor station of the particles deposition assembly of the system according to any of clauses 1 to 39.

41. A particles deposition sensor station constructed for cooperation with a disposable of the particles deposition assembly of the system according to any of clauses 1 to 39.

42. A method for detecting airborne particles deposition, the method comprising:

releasable holding a particles deposition accumulating disposable with a body portion of radiation transmissive material and forming a particles accumulation surface to accumulate depositing particles with a holder on the outside of a particles deposition sensor station; providing a radiation beam from a radiation device of the sensor station to the disposable;

detecting with a radiation detector of the sensor station the radiation beam traversing through the disposable by receiving the radiation beam on a radiation detector;

receiving an interference pattern caused by interference between an unscattered portion of the radiation beam and the radiation beam being scattered from:

one or more calibration marks provided at a plane of at least one of a radiation transmissive body portion of the disposable and an optical component of the sensor station through which said radiation traverses; and,

a particle deposited on the particles accumulation surface of the disposable on the radiation detector; and,

processing the interference pattern in a computer to calibrate the disposable and/or the sensor station and to detect any depositing particles on the particles accumulation surface.

43. The method according to clause 42, wherein the method comprises calibrating the size of a depositing particle by creating an interference pattern on the radiation detector by interference of a portion of the radiation beam being scattered by the one or more calibration marks and an unscattered portion of the radiation beam.

44. The method according to any of clauses 42 to 43, wherein the method comprises replacing the disposable from the holder of the sensor station with another disposable.

45. The method according to any of clauses 42 to 44, wherein the method comprises calculating with image data from the detector a number of particles accumulated on the disposable.

46. The method according to clause 45, wherein the method comprises:

storing in a memory of the computer an indication of a number of particles calculated at a first moment;

calculating with a image data received at a second, later moment from the radiation detector a new indication of a number of particles accumulated on the particles deposition detection disposable after a time interval; and,

deriving from the new indication of the number of particles accumulated on the disposable and the stored indication a rate of particles deposition in the time interval between the first and the second moment.

47. The method according to clause 46, wherein the method comprises comparing the rate of particles deposition with a range or value for an acceptable rate of particles deposition and activating an alarm if the rate of particles deposition is higher than the acceptable range or value. 48. The method according to any of clauses 42 to 48, wherein the method comprises calculating with image data from the radiation detector an indication of the size of particles accumulated on the disposable.

49. The method according to any of clauses 42 to 48, wherein the method comprises transmitting an output signal comprising an indication of the number of particles accumulated on the disposable or an indication of the size of particles accumulated on the disposable.

50. The method according to any of clauses 42 to 49, wherein the method comprises transmitting primary data of the radiation detector from the sensor station with a primary transmitter and receiving the primary data with a primary receiver provided to a stand alone unit positioned away from the sensor station.

51. The method according to clause 50, wherein the method comprises transmitting image data representing an interference pattern received at the radiation detector as the primary data.

52. The method according to clause 50 or 51 wherein the method comprises positioning at least one sensor station in a cleanroom and positioning the stand alone unit outside the cleanroom.

53. The method according to any of clauses 50 to 53, wherein the method comprises calculating with the image data from the radiation detector a number of particles accumulated on the disposable at the stand alone unit.

54. The method according to any of clauses 50 to 54, wherein the method comprises transmitting secondary data with a secondary transmitter provided to the stand alone unit to a secondary receiver provided to the sensor station.

55. The method according to clause 54, wherein the method comprises transmitting an alarm activation signal as secondary data via the secondary transmitter to the secondary receiver of the sensor station activating an alarm.

56. The method according to any of clauses 43 to 56, wherein the method comprises replacing an empty battery provided to the sensor station with a charged battery.

Embodiments of the invention will be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which:

Fig 1 depicts an airborne particles deposition detection assembly to detect air particles deposition according to an embodiment;

Figure 2 depicts different parts that together form a particles deposition sensor station of the assembly of figure 1 ;

Figure 3 depicts a radiation beam traversing thought the sensor station and the particles deposition accumulation disposable of the assembly of figure 1 ; Figure 4a depicts a side view, 4b a 3D view and 4c a top view on a disposable 3 for the assembly of figure 1 ;

Figure 5a, 5b and 5c depict the pattern and size of the calibration markers on an disposable according to an embodiment for use in the assembly of figure 1 ; and,

Figure 6 depicts an airborne particles deposition detection system to detect air particles deposition with the assembly of figure 1.

Fig 1 depicts an airborne particles deposition detection assembly 1 to detect air particles deposition in a space, such as a cleanroom e.g. an operation room, a clean production room or a food processing room.

The assembly 1 comprises:

a disposable 3 with a body portion 5 of radiation transmissive material the body portion 5 forming a particles accumulation surface on which in use depositing particles falling in the direction of arrow A from the air accumulate; and,

a particles deposition sensor station 7 to detect particles deposition on the disposable

3.

The sensor station 7 is provided with a holder 9 adapted to releasable hold the disposable 3. The holder 9 is constructed to hold the disposable 3 stationary in the holder. If the disposable 3 moves in the holder during a detection cycle the detection of particles may be disturbed.

The holder 9 comprises a void or recess provided on the outside of the housing 11 to hold the disposable 5 stationary at the exterior of the housing 11. The housing 11 may be provided with a bar 12 to improve holding the disposable 3 stationary in the void or recess.

The sensor station 7 may be provided with indication lights 13 indicating a state of the sensor station 7, for example to indicate that the power is on, the presence of a correctly positioned disposable 3 in the holder 9, that a battery is almost finished or the detection of particles with radiation.

Figure 2 depicts different parts that together form the sensor station 7 of figure 1. The sensor station comprises a housing 7 in which a battery 15 may be provided to provide electrical power 15. The housing may be provided with a window 17a, b.

The window 17a, b may be provided with a window pane of radiation transmissive material 19. In this way the interior of the housing 11 may be protected for depositing particles entering the housing 11. The radiation transmissive material 19 may be provided with a radiation band pass filter to block any radiation different than the radiation of a radiation device 21. Radiation from other sources in the environment of the sensor station 7 may disturb a radiation detector 23. By providing the radiation band pass filter those other sources may be filtered out before they reach the radiation detector 23.

The radiation 21 and the radiation detector 23 may be provided in a frame 25 which may be moved inside the housing 11 during assembling. Indication lights 13 may also be provided to the frame 25. The window 17a, b may be left open to create an open window. If the disposable is at least partially covering the open window the interior of the housing 11 will be protected for depositing particles anyway.

The window 17a, b is divided in a first window 17a to provide the radiation beam from the radiation device 21 inside the housing 11 to the disposable outside the housing 11 and a second window 17b to provide the radiation beam from the particles deposition accumulation disposable outside the housing to the radiation detector 23 inside the housing 11. The sensor station 7 is provided with a side panel 27.

Figure 3 depicts a radiation beam traversing thought the sensor station 7 and the particles deposition accumulation disposable 3. The radiation device 21 radiates a radiation beam 29 via the radiator optics comprising first mirror 31 , first lens 33 and second mirror 35 to the disposable 3. The radiation detector 23 receives the radiation beam 29 via the detector optic comprising second lens 37, third mirror 39 and fourth mirror 41 from the particles deposition accumulation disposable 3. The radiator optics and the detector optics are securely mounted in the frame 25. The first window 17a provides the radiation beam 29 from the radiation device 21 inside the housing to the disposable 3 outside the housing and the second window 17b provides the radiation beam 29 from the particles deposition

accumulation disposable 3 outside the housing to the radiation detector 23 inside the housing.

The radiation device 21 e.g. laser or a light emitting diode is providing a radiation beam 29 with substantially monochromatic radiation. Monochromatic radiation will give the best interference patterns on the radiation detector 23. The smaller the wavelength the better the resolution. For example, a 405 nanometer wavelength laser of 5 milliwatt may be used as the radiation device 21. Alternatively, any optical radiation with different amounts of power and wavelengths may be used. For example, a wavelength between 365 and 700 nm may be used for the radiation device. The holder 9 of the sensor station 7 is adapted to releasable hold the disposable 3 with its body portion 5 forming the particles accumulation surface in the radiation beam 29 traversing from the radiation device 21 to the radiation detector 23. The holder 9 comprises a void 43 provided on the outside of the housing to hold the disposable 3 stationary.

The radiation detector 23 receives an interference pattern caused by interference between an unscattered portion of the radiation beam 29 and a portion of the radiation beam being scattered from a calibration mark 45 being provided to the body portion 5 of the disposable 3 to calibrate the system. By having the calibration mark 45 on the body portion 5 of the disposable 3 the calibration mark 45 may be replaced together with the disposable 3 such that it is less likely that it gets contaminated before it is used for the first time to calibrate the system.

Alternatively, the radiation detector 23 receives an interference pattern caused by interference between an unscattered portion of the radiation beam 29 and a portion of the radiation beam being scattered from a calibration mark being provided at a plane of at least one of the radiator optics, the detector optics and the window pane e.g. radiation transmissive material 19 provided in the windows 17a, b to calibrate the system. An advantage being that the disposable can be produced without calibration marks making the production process more simple.

The radiation detector 23 also receives an interference pattern caused by interference between an unscattered portion of the radiation beam 29 and a portion of the radiation beam being scattered from a particle 47 deposited on a particles accumulation surface 49 of the disposable 3 to detect any depositing particles on the particles accumulation surface 49. The disposable 3 may stay stationary in the sensor station 7 so that it doesn't need to be moved from a location where the detection took place to the sensor station 7. Contamination with particles or loss of particles on the disposable 3 during the transfer is thereby minimized. By having the calibration mark 45 on the body portion of the disposable the calibration mark 45 may be replaced together with the disposable such that it is less likely that it gets contaminated before it is used for the first time to calibrate the system. The sensor station 7 comprises a holder 9 to releasable hold the disposable 3. The disposable 3 doesn't need to be moved from a location where the detection took place to the sensor station 7 such that the risk of contamination with particles or loss of particles on the disposable 3 during the transfer is minimized. The radiation detector 23 may be a CCD camera, which is simple and effective means for capturing the image data of the inference pattern caused by interference between the radiation beam being scattered from a particle deposited on the particles accumulation surface 49 of the particles deposition accumulation disposable 3 and the unscattered radiation beam.

The image data of the CCD camera may be shown on a visual display to allow a user to interpret the interference pattern. The particles accumulation surface 49 of the disposable 3 is divided in multiple particles accumulation sub-surfaces 51 a... f, each to accumulate depositing particles and the multiple sub-surfaces 51 a... f are positioned in different planes behind each other in a first direction substantially parallel to the radiation beam 29. The first calibration mark 45a may be provided on a first particles accumulation sub-surface 51a and a second calibration mark 45f on a second particles accumulation sub-surface 51f of the multiple sub-surfaces 51a...51f. The second calibration mark 45f maybe provided on a last sub-surface 51f of the multiple sub-surfaces 51a...51f positioned behind each other in the first direction. In this way by detecting the calibration marks it becomes possible to detect a position of the disposable 3 in the holder 9 of the sensor station 7 with a high accuracy.

The first particles accumulation sub-surface 51a may receive the radiation beam of the radiation device first and the last particles accumulation sub-surface 51f may receive the radiation beam 29 last from all the sub-surfaces 51 a...51f and the calibration mark 45a on the first particles accumulation sub-surface may be positioned closer to a centre of the first particles accumulation sub-surface 51 a than the calibration marks 45f on the last particles accumulation surface 51f. The last particle accumulating sub-surface 51f may be closer to the radiation detector 23 while the first particle accumulating sub-surface 51a is further away from the radiation detector 23. If the diffraction angle is taken constant (for example by taking a calibration mark 45f with the same size as the calibration mark 45a) the spread of the diffracted energy at the detecting surface of the radiation detector 23 is larger if the diffraction occurs further away from the radiation detector 23 (for example at the first particle accumulating sub-surface 51a). By providing the calibration marks 45aa more at the centre of the radiation beam 29 (compared to the calibration mark 45a) although the spread may be larger the detecting surface of the radiation detector 23 still may receive sufficient diffracted energy to use the calibration mark 45aa.

Another solution is having larger calibration marks 45a (with consequently smaller diffraction angels) on the first particle accumulating sub-surface 51a more of the diffracted energy may reach the detecting surface of the radiation detector 23 than if smaller calibration marks were used (with consequently larger diffraction angels). Closer to the radiation detector 23 smaller calibration marks may be used because although the diffraction angle is larger the relatively short distance to the radiation detector 23 still assures that enough of the diffracted energy will reach the detecting surface of the radiation detector 23.

The calibration marks 45a and 45aa on the first particles accumulation surface 51a are different of size and differently positioned than the calibration marks 45f on the last particles accumulation sub-surface 51 f. The diffraction angle and the position with respect to the radiation detector 23 may be taken into account to optimize the amount of diffracted energy received by the radiation detector 23.

The sub-surfaces 51a to 51f of the disposable 3 are tilted with respect to a first direction parallel to the radiation beam between 10 to 80°, preferably between 30 to 60° and most preferable between 40 to 50°. T

The sub-surfaces 51a to 51f of the disposable 3 are divided over two groups of subsurfaces, a first group of sub-surfaces 51 b, d, f tilted with respect to the first direction between 10 to 80°, preferably between 30 to 60° and most preferable between 40 to 50° and a second group of sub-surfaces 51a, c, e tilted with respect to the first direction between -10 to -80°, preferably between -30 to -60° and most preferable between -40 to -50°. A sub-surface of the first group of sub-surfaces e.g. 51b may be connected to a sub-surface of the second group of sub-surfaces e.g. 51c in an inverted V arrangement when viewed from a side. The first and second group of sub-surfaces may be positioned alternatingly behind each other in the first direction. The sub-surfaces 51a to 51f may compose a continuously closed surface for the particle accumulating surface 49.

The common plane in which the calibration marks are provided may be the particles accumulation surface 49, its sub-surfaces 51a to 51f, or any other portion of the disposable through which the radiation beam traverses. By having the particles accumulating close or on the same surface as where the calibration marks 45 are provided the distance between the marks 45 and the particles is kept small increasing the accuracy of the system.

Alternatively, the common plane in which the calibration marks 45 are provided is on a different surface than the particles accumulation surface 49. The radiation device 21 is a pulsed radiation device to radiate a pulsed radiation beam 29 and the radiation detector 23 is adapted to take pictures with image data of the

interference pattern created with the pulsed radiation beam. The system may be adapted to take pictures in a periodic manner, for example in any adjustable interval e.g. of 1 , 5, 10, 15, 30, or 60 minutes. The radiation device 21 and the radiation detector 23 may be switched off in between the interval if the system is not function so as to safe energy and not to dissipate any heat which may effect airflow in the vicinity of the sensor station 7.

The disposable 3 may comprise a RFID chip for identification of the disposable 3 to a RF receiver provided in the sensor station 7. Identification of the disposable 3 may help the sensor station 7 to identify the calibration marks 45 on the disposable 3. It also may help to determine how much particles deposition has occurred during a particular time interval.

The body portion 5 of the particles deposition accumulation disposable 3 may be provided with a plurality of calibration marks 45 positioned in a common plane. The plurality of calibration marks 45 may be used to define a distance in a common plane in the particles deposition accumulation disposable 3. The plurality of marks 45 may also be used to determine whether the particles deposition accumulation disposable 3 is correctly positioned in the holder 9.

The assembly 1 is provided with a detector output 52 to output image data

representing the interference pattern received on the radiation detector 23, the detector output being operably connectable with a computer 53 comprising a processor P connected to a memory M. The memory is provided with software which when run on the processor calculates with the image data from the radiation detector 23 at least one of:

an indication of a number of particles accumulated on the particles deposition accumulation disposable 5;

an indication of a size of the particles accumulated on the particles deposition accumulation disposable 5; and,

an alarming activation signal if the number of particles accumulated on the particles deposition accumulation disposable 5 is higher than a predetermined threshold value.

Figure 4a, 4b and 4c depict a disposable 3 comprising a non-continue surface 9 to accumulate depositing particles and being transmissive for a radiation beam wherein a calibration mark 45a is being provided to the body portion 5 of the disposable 3. The calibration mark 45a may assure a fast calibration of the disposable 3. The surface 9 of the disposable 3 may be split in multiple sub-surfaces 51 a... f each to accumulate depositing particles and the multiple sub-surfaces 51 are positioned behind each other in a first direction 55. A first calibration mark 45a may be provided on a leading sub-surface 51 a and a second calibration mark 45f may be provided on another sub-surface 51f of the multiple sub-surfaces positioned behind each other in the first direction 55. The second calibration mark 45f may be provided on a last sub-surface 51f of the multiple sub-surfaces positioned behind each other in the first direction. The sub-surfaces of the disposable 3 may be tilted with respect to the first direction between 10 to 80°, preferably between 30 to 60° and most preferable between 40 to 50°. The sub-surface of the disposable may be divided over two groups of sub-surfaces, a first group of sub-surfaces 51 b, 51 d, and 51f tilted with respect to the first direction between 10 to 80°, preferably between 30 to 60° and most preferable between 40 to 50° and a second group of sub-surfaces 51a, 51c, and 51e tilted with respect to the first direction between -10 to -80°, preferably between -30 to -60° and most preferable between -40 to -50°. The first and second group of subsurface are positioned alternatingly behind each other in the first direction. The disposable may comprise a RFID chip 57 for identification of the disposable 3 to a RF receiver provided in the base unit.

Figure 5a, 5b and 5c depict the pattern and size of the calibration markers on a disposable 3 for use in the assembly of figure 1. Figure 5a depicts a leading sub-surface 51a and figure 5b depicts a last sub-surface 51f seen from a direction perpendicular to the sub- surface. Figure 5c depicts a table with a reference number M to the calibration mark, the size of the calibration mark in micrometres (Mu) and on which sub-surface (Sub-S) 51a or 51f in figure 3 and 4 the calibration mark is positioned. The reference numbers of the marks in figure 5c refers to the calibration marks in figure 5a and 5b so that the actual size and position of all the calibration marks on the sub-surfaces 51 a and 51 f is shown.

The plurality of calibration marks on the sub-surface may comprise a first group of first size calibration marks with a first size. For example, calibration marks 83 to 87 with a size of 10 micrometre on sub-surface 51a or calibration marks 71 to 74 with a size of 25 micrometre on sub-surface 51f. By providing calibration marks with a known first size it becomes possible to calibrate the size of particles deposited on the sub-surfaces.

The plurality of calibration marks may comprise a second group of second size calibration marks with a second size larger than the first size. For example, calibration marks 75 to 78 with a size of 25 micrometre on sub-surface 51 a. By providing calibration marks with a different size it becomes possible to calibrate the size of particles more accurate. It also becomes possible to differentiate between calibration marks using the size as an identifier. The plurality of calibration marks comprise a third group of third size calibration marks with a third size larger than the first and second size. For example, calibration marks 80 and 81 with a size of 200 micrometre on sub-surface 51a. By providing calibration marks with a first, a second and a third size it becomes possible to calibrate the size of particles even more accurate and identify even more calibration marks. The calibration marks may have a size between 1 and 1000 micrometre, preferably between 5 and 500 micrometre and most preferable between 10 and 200 micrometre.

The first, second and/or third group of calibration marks may comprise three calibration marks positioned along a straight line. For example, three of the five calibration marks 83 to 87 with a size of 10 micrometre are positioned along a straight line on subsurface 51 a. In this way the line is over-determined making it possible to calculate a deviation of the calibration marks themselves. At least on of the first, second and third group of calibration marks may comprise four calibration marks, each positioned on a corner of a quadrangle. The quadrangle may be a square or a rhombus. For example, calibration marks 75 to 78 with a size of 25 micrometre on sub-surface 51a form a rhombus. Calibration marks 71 to 74 with a size of 25 micrometre on sub-surface 51f form a square. The quadrangles may be used to define a quadrangle on a common plane with a certain size, which may be used to calibrate for example a particles deposition accumulating surface.

The first, second and/or third group of calibration marks are positioned in pairs of two. Fro example, calibration marks 71 to 74 with a size of 25 micrometre on sub-surface 51f form four pairs of two marks. Calibration marks 80 and 81 with a size of 200 micrometre on subsurface 51 a form a single pair of two calibration marks. In this way a distance and a direction as well as a position may be calibrated.

The common plane can be divided in two imaginary halves by an axis of symmetry and one of the groups of calibration marks (for example 79 and 83 on sub-surface 51 f) can be positioned in one of the two imaginary halves. With the alignment marks positioned asymmetrical it becomes possible to calibrate which side of the disposable 3 is where.

The plurality of calibration marks comprise calibration marks with different shapes. The shapes may for example enhance diffraction in a certain direction. In this way it becomes possible to recognize different calibration marks. Which may be helpful to identify the calibration mark and/ or the disposable with the system. Figure 6 depicts a top view on an airborne particles deposition detection system to detect air particles deposition with multiple assemblies 1. The assemblies are provided with the disposable 3 and the sensor station 7 to detect any particles deposition on the disposable 3.

The radiation detector is connected to a primary transmitter 101 to transmit primary data from the sensor station 7 to a stand alone unit 103 positioned away from the sensor station 7 and provided with a primary receiver 105 to receive primary data transmitted from the assembly 1. By providing the stand alone unit 103 away from the sensor station 7 there is no need to have the heat (and consequently turbulence) producing computer in the cleanroom.

The stand alone unit 103 comprises a secondary transmitter (combined with primary receiver 105) and the sensor station 7 comprises a secondary receiver (combined with primary transmitter 101) to receive secondary data transmitted from the stand alone unit 103 to the sensor station 7. The sensor station 7 is provided with an alarm 107 connected to the secondary receiver and the stand alone unit may be constructed and arranged to transmit secondary data comprising an alarm activation signal via the secondary transmitter to the secondary receiver of the sensor station 7 to activate the alarm 107. The alarm may give an acoustic signal or a visual signal or both to warn the users for particles deposition near the sensor station 7.

The sensor station 7 may be provided with a battery holder for holding a battery to provide electricity to the sensor station. The stand alone unit 103 may be provided with a battery charger 109 for charging a battery. By providing batteries to the sensor station 7 no separate energy connector may be necessary for the sensor station 7.

The stand alone unit 103 is provided with a computer 111 connected (with a wire or wireless) to the primary receiver to receive and process image data from the radiation detector of the sensor station 7. The computer 111 may comprise a processor connected to a memory and the memory is provided with software which when run on the processor performs calculations on the image data from the radiation detector, e.g. to provide an indication for the number of particles accumulated on the disposable 3, an indication of the size of particles accumulated on the disposable 3 or an indication of the size and or position of a calibration mark provided to the disposable 3.

The computer may be provided inside the stand alone unit 103 to process image data from the radiation detector of the sensor station 7 inside the stand alone unit 103. The computer may comprise a processor connected to a memory and the memory is provided with software which when run on the processor performs calculations on the image data from the radiation detector, e.g. to provide an indication for the number of particles accumulated on the disposable 3, an indication of the size of particles accumulated on the disposable 3 or an indication of the size and or position of a calibration mark provided to the disposable 3. The memory may also be used to store the particle detection results, either in their raw image date format or after being processed.

The processor may be connected to a system output to transmit an output signal which output signal is the result of image data processed by the processor. The output signal may be used to depict a graph or a report on a visual screen 113 with the aid of the computer system.

These and other aspects, features and advantages will become apparent to those of ordinary skill in the art from reading the description and the appended claims. For the avoidance of doubt, any feature of one aspect of the present invention may be utilised in any other aspect of the invention. It is noted that the examples given in the description below are intended to clarify the invention and are not intended to limit the invention to those examples per se.

Claims

- a particles deposition accumulating disposable with a body portion of radiation transmissive material, the body portion forming a particles accumulation surface on which in use depositing particles from the air accumulate;

- a particles deposition sensor station adapted to detect particles deposition on the particles accumulation surface; the sensor station comprising:

- a holder adapted to releasable hold the disposable;

- a radiation device adapted to emit a radiation beam to the disposable; and,

- one or more calibration marks provided on at least one of a radiation transmissive body portion of the disposable and, if present, a radiation transmissive component of the sensor station through which said radiation beam traverses, allowing to calibrate the system; and from:

- any particles deposited on the particles accumulation surface of the disposable, allowing to detect said deposited particles.

2. The system according to claim 1 , wherein a radiation transmissive body portion of the disposable is provided with said one or more calibration marks, preferably said one or more calibration marks being arranged thereon so as to be irradiated by the portion of the traversing radiation beam that irradiates the accumulation surface.

3. The system according to claim 1 or 2, wherein a plurality of calibration marks is located in a common plane, e.g. in a plane that is parallel to or coincides with the

accumulation surface of the disposable or a sub-surface thereof.

4. The system according to any one of claims 1 - 3, wherein a plurality of calibration marks is provided having a size between 1 and 1000 micrometers, preferably between 5 and 500 micrometers, more preferably between 10 and 250 micrometers.

5. The system according to any one of claims 1 - 4, wherein a plurality of calibration marks is provided comprising at least a first group of first calibration marks, preferably located in a common plane, said first calibration marks each having a first size, e.g. between 5 and 20 micrometers, and wherein possibly there are also provided one or more of:

- a second group of second calibration marks each having a second size larger than the first size, e.g. between 25 and 70 micrometers, preferably said first and second groups of calibration marks being located in a common plane,

- a third group of third calibration marks each having a third size larger than the first size and than the second size, e.g. between 75 and 250 micrometers, preferably said third group of calibration marks being located in a common plane with said first and second groups of calibration marks.

6. The system according to claim 5, wherein at least one of the first, second, and third group of calibration marks comprises three calibration marks arranged in a common plane and positioned along a straight line.

7. The system according to claim 5 or 6, wherein at least one of the first, second, and third group of calibration marks comprises four calibration marks arranged in a common plane and each positioned on a corner of an imaginary quadrangle.

8. The system according to any one of claims 5 - 7, wherein in at least one of the first, second, and third group of calibration marks, some of the calibration marks are positioned in pairs of two that are closer to one another than to other calibration marks of said group.

9. The system according to at least claim 3, wherein the common plane is divided in two imaginary halves by an imaginary axis and wherein the calibration marks in said two imaginary halves are not symmetrical relative to said axis.

10. The system according to any of claims 2 to 8, wherein a plurality of calibration marks is located in a common plane, and wherein calibration marks with a relatively smaller size are provided close to a centre of said common plane and calibration marks with a relatively larger size are provided further away from said centre.

11. The system according to any of the preceding claims, wherein at least the body portion of the disposable forming the particles accumulation surface and the body portion of the disposable that is provided with the one or more calibration marks are injection moulded of plastic material as a unitary plastic body, preferably the entire disposable being injection moulded as a unitary plastic body.

12. The system according to any of the preceding claims, wherein the particles accumulation surface of the disposable is formed by multiple particles accumulation subsurfaces, and said sub-surfaces being positioned behind each other in a first direction substantially parallel to the radiation beam.

13. The system according to claim 12, wherein a first calibration mark or a group of calibration marks is provided on a leading sub-surface and a second calibration mark or group of calibration marks is provided on a second sub-surface, preferably wherein the second calibration mark or group of calibration marks is provided on a last sub-surface of the disposable as seen in the first direction substantially parallel to the radiation beam.

14. The system according to claim 13, wherein the leading sub-surface receives the radiation beam first and the last sub-surface receives the radiation beam last from all the subsurfaces and wherein the majority of the calibration marks on the leading sub-surface are different of size and differently positioned than the majority of the calibration marks on the last sub-surface.

15. The system according to any of the preceding claims, wherein the system is provided with a detector output device to output image data representing the interference pattern received on the radiation detector, the detector output device being operably connectable with a computer comprising a processor connected to a memory and the memory is provided with software which when run on the processor performs calculations with the image data from the radiation detector to calculate at least one of:

- an alarm activation signal if the indication of the number and/or size of the particles accumulated on the accumulation surface of the disposable is outside an allowable range or value.

16. The system according to any of the preceding claims, wherein the sensor station comprises a housing having one or more housing parts, preferably a single housing, wherein the radiation device and the radiation detector are arranged within said housing, and wherein the holder is adapted to releasable hold the disposable externally of the housing, preferably such that the accumulation surface faces upwards so as to receive thereon depositing particles while being held stationary by the holder relative to the housing, and

wherein at least one window is provided in the housing to provide the radiation beam from the radiation device to the accumulation surface and further to the radiation detector to detect any deposition particles on the accumulation surface of the disposable.

17. The system according to claim 16, wherein each window is provided with a radiation transmissive window pane, and wherein, preferably, each window pane is embodied as a radiation band pass filter to block any radiation different than the radiation beam from entering the housing or housing parts.

18. The system according to any of the preceding claims wherein the sensor station comprises a primary transmitted to which the radiation detector is connected in order to transmit primary image data from the sensor station; and,

wherein the system further comprises a stand alone unit positioned away from the sensor station and provided with a primary receiver to receive primary image data transmitted from the sensor station, preferably said stand alone unit being provided with said computer according to claim 15.

19. A particles deposition accumulating disposable constructed for cooperation with a sensor station of the particles deposition assembly of the system according to any of claims 1 to 18.

20. A particles deposition sensor station constructed for cooperation with a disposable of the particles deposition assembly of the system according to any of claims 1 to 18.

21. A method for detecting airborne particles deposition, the method preferably using the system of any of claims 1 - 18, the method comprising:

providing a radiation beam from a radiation device of a sensor station to the disposable so as to traverse said body portion of radiation transmissive material that forms the accumulation surface; detecting with a radiation detector of the sensor station the radiation beam traversed through the accumulation surface of the disposable by receiving the radiation beam on the radiation detector;

-particles deposited on the accumulation surface of the disposable;

and,