Airborne particle sensor

Abstract

An airborne particle sensor 4000 includes a sample holder 4004, light diffuser 4006 and detector 4002. The sample holder 4004 holds a sample of the airborne particle such as dust, pollen or other allergens. The sample holder 4004 and the optical path between the sample holder 4004 and the detector 4002 are enclosed within the light diffuser 4006. The light diffuser 4006 may be a prism such as a pyramidal frustrum (fig 5). The light diffuser 4006 may evenly distribute light from a light source 4008 across the sample holder 4004. There may be multiple light sources 4008 at different locations which may use different wavelengths to detect different types of particles. The detector 4002 may be a photodiode or MEMS for detecting scattered light from the airborne particles on the sample holder 4004. The sample holder 4004 may be a transparent slide or a filter. There may be a housing to reduce external light from reaching the sample holder 4004.

Description

BACKGROUND Field of the Disclosure The present invention relates to an airborne particle sensor and associated sensing device. Description of the Related Art The "background" description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in the background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly or impliedly admitted as prior art against the present invention. Allergic reactions to particles are debilitating and, in some instances, can be fatal. Airborne particle sensors can be used to detect and measure particles in the air. These particles can include dust mites, pollen, animal dander, mould and other particulate contaminants. Current techniques for particle sensing involve the use of a particle sensor of airborne particles with a light source and a photodetector to detect the presence of particles based on the scattering of light by the particles. However, the accuracy of these particle sensors can be affected by variations in the direction of the light. Furthermore, optical interference is also a common challenge with airborne particle sensors. This can make it difficult to provide accurate and reliable detection of particles when using an airborne particle sensor. It is an aim of the disclosure to address these issues. SUMMARY: Embodiments of the disclosure are defined by the claims. Further aspects of the disclosure are defined by the dependent claims. According to embodiments of the present disclosure, more accurate and reliable detection of particles when using an airborne particle sensor can be provided. It will be appreciated that the present disclosure is not particularly limited to these advantageous technical effects. Other advantageous technical effects are provided as will be apparent to the skilled person when reading the disclosure. BRIEF DESCRIPTION OF THE DRAWINGS A more complete appreciation of the disclosure and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein: Figure 1 illustrates an apparatus in accordance with embodiments of the disclosure; Figure 2 illustrates a sensing device in accordance with embodiments of the disclosure; Figure 3 illustrates an imaging device in accordance with embodiments of the disclosure; Figure 4 illustrates a particle sensor in accordance with embodiments of the disclosure; Figure 5 illustrates a light diffuser in accordance with embodiments of the disclosure; Figure 6 illustrates a light diffuser in accordance with embodiments of the disclosure; Figure 7 illustrates a particle sensor in accordance with embodiments of the disclosure; Figure 8 illustrates a particle sensor in accordance with embodiments of the disclosure; and Figure 9 illustrates an example of particle detection in accordance with embodiments of the disclosure. DESCRIPTION OF THE EMBODIMENTS Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views. The word "exemplary" or "embodiment" is used herein to mean "serving as an example, instance, or illustration." Any implementation or aspect described herein as "exemplary" or as an "embodiment" is not necessarily to be construed as preferred or advantageous over other aspects of the disclosure. Likewise, the term "aspects" does not require that all aspects of the disclosure include the discussed feature, advantage, or mode of operation. Embodiments will now be described in detail with reference to the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the aspects described herein. It will be apparent, however, to one skilled in the art, that these and other aspects may be practiced without some or all of these specific details. In addition, well known steps in a method of a process may be omitted from flow diagrams presented herein in order not to obscure the aspects of the disclosure. Similarly, well known components in a device may be omitted from Figures and descriptions thereof presented herein in order not to obscure the aspects of the disclosure. Referring to Figure 1, an apparatus 1000 according to embodiments of the disclosure is shown. Typically, an apparatus 1000 according to embodiments of the disclosure is a computer device such as a personal computer or a terminal connected to a server. Indeed, in embodiments, the apparatus may also be a server. The apparatus 1000 is controlled using a microprocessor or other processing circuitry 1002. In some examples, the apparatus 1000 may be a portable computing device such as a mobile phone, laptop computer or tablet computing device. The processing circuitry 1002 may be a microprocessor carrying out computer instructions or may be an Application Specific Integrated Circuit. The computer instructions are stored on storage medium 1004 which maybe a magnetically readable medium, optically readable medium or solid state type circuitry. The storage medium 1004 may be integrated into the apparatus 1000 or may be separate to the apparatus 1000 and connected thereto using either a wired or wireless connection. The computer instructions may be embodied as computer software that contains computer readable code which, when loaded onto the processor circuitry 1002, configures the processor circuitry 1002 to perform a method according to embodiments of the disclosure. Additionally, an optional user input device 1006 is shown connected to the processing circuitry 1002. The user input device 1006 may be a touch screen or may be a mouse or stylist type input device. The user input device 1006 may also be a keyboard or any combination of these devices. In some examples, the user input device 1006 may be a microphone or other the like. As such, a user may be able to provide user input using their voice (e.g. by speaking a control word or command). A network connection 1008 may optionally be coupled to the processor circuitry 1002. The network connection 1008 may be a connection to a Local Area Network or a Wide Area Network such as the Internet or a Virtual Private Network or the like. The network connection 1008 may be connected to a server allowing the processor circuitry 1002 to communicate with another apparatus in order to obtain or provide relevant data. The network connection 1002 may be behind a firewall or some other form of network security. Additionally, shown coupled to the processing circuitry 1002, is a display device 1010. The display device 1010, although shown integrated into the apparatus 1000, may additionally be separate to the apparatus 1000 and may be a monitor or some kind of device allowing the user to visualise the operation of the system. In addition, the display device 1010 may be a printer, projector or some other device allowing relevant information generated by the apparatus 1000 to be viewed by the user or by a third party. Figure 2, illustrates a sensing device in accordance with embodiments of the disclosure. More specifically, Figure 2 illustrates a schematic block diagram of an embodiment of a sensing device 100 that automates the capture and imaging of microscopic particles in the ambient air for continuous monitoring of allergen levels. The sensing device 100 includes a receptacle 102 having a fan 104 and a collection plate 106. The fan 104 is configured to generate an air flow through the receptacle 102 and force the particles in the air flow towards the collection plate 106. For example, the air flow carries airborne particles through one or more inflow vents 108 into the receptacle 102 and onto the collection plate 106. The collection plate 106 is made of a transparent material and may be covered with an electrostatic coating configured to attract the airborne particles. The air flow then exits one or more outflow vents in the receptacle 102. Airborne particles may land naturally over time on the collection plate 106, or the airborne particles may be directed to the collection plate 106. In some examples, particles may land on the collection plate 106 under the effect of gravity. Alternatively, for example, the airborne particles may be directed to the collection plate 106 using the fan 104 to push or pull air flow to the collection plate 106. In an embodiment, the collection plate 106 may have a positive charge to attract particles. In one embodiment, the fan 104 may generate a fixed air flow mimicking lung capacity of human breathing, e.g. at approximately 8 liters per min. The speed of the fan 104 is set to generate an air flow to the collection plate 106 of approximately 8 liters / min. The air flow thus provides an estimate of the air inhaled by a user and the actual particle inhalation of a user. In another embodiment, the air flow generated by the fan 104 may be faster (e.g., for faster air quality assessment) or slower depending on the use and environment of the sensing device 100. For example, for a workplace or factory environment, the speed of the fan 104 may be controlled to a faster speed. In an outdoor environment with heavy particle concentration, the fan 104 may be slower. The sensing device 100 includes an imaging device 110 configured to capture images of the airborne particles on the collection plate 106. In some examples, the imaging device may form part of a particle sensor in accordance with embodiments of the disclosure. The particle sensor and imaging device will be described in more detail hereinafter. A brush, high impaction fan or other means may be implemented to periodically clean the collection plate 106 of airborne particles. In another embodiment, sticky tape or other surface may be implemented for collecting the airborne particles. A control module 112 includes one or more processing circuits and memory devices. The processing circuit includes one or more processing devices, such as a microprocessor, micro-controller, digital signal processor, microcomputer, central processing unit, field programmable gate array, programmable logic device, state machine, logic circuitry, analog circuitry, digital circuitry, and / or any device that manipulates signals (analog and / or digital) based on hard coding of the circuitry and / or operational instructions. The one or more memory devices may include a read-only memory, random access memory, volatile memory, non-volatile memory, static memory, dynamic memory, flash memory, cache memory, and / or any non-transitory memory device that stores digital information. The storage device stores one or more instructions or programs which when performed by the one or more processing circuits, instructs the sensing device 100 to perform one or more functions described herein. The control module 112 may further include a wireless and / or wireline transceiver 114 configured to communicate over a WLAN, Bluetooth, cellular network or other WAN or short-range network. The transceiver 114 may communicate data to and from a central server over a WAN and download remote software updates or commands from the central server. In some examples, the control module 112 may be implemented as an apparatus 1000 described with reference to Figure 1 of the present disclosure. The sensing device 100 may also include other sensors 120, such as pollution detectors, temperature sensors, humidity detector, barometric pressure, etc. Figure 3 illustrates an imaging device in accordance with embodiments of the disclosure. More specifically, Figure 3 illustrates a schematic block diagram of an embodiment of the imaging device 110 in more detail. The imaging device 110 includes an image sensor 204, such as CMOS, and an illumination system 202. The illumination system 202 may optionally include one or more light sources (such as LEDs) configured to emit light in one or more spectrums, e.g. one or more of visible, ultraviolet (UV), near infrared or infrared light. In other examples, the imaging device 110 may use a natural source of illumination (e.g. the ambient light from outside the sensing device). In addition, a number of different light sources may be used in combination. For example, a visible light may be used first and then a UV light may be applied. In some examples, the UV light may be applied immediately after the application of the visible light. Analysis performed with the visible light and the UV light may then be combined (e.g. superimposed or compared) for more accurate identification of the particles. The optical system 206 includes one or more lenses for magnification of the particles on the collection plate 106. The focus controller 208 includes mechanical and / or electronic mechanisms to adjust a focus of the lenses. The control module 112 or the focus controller 208 or a combination thereof may control the focus of the optical system 206 as described herein. The focus controller 208 may include a combination of auto-focus or manual focus of the optical system. In an embodiment, the focus controller 208 may automatically detect a focus for imaging a variety of different sized particles on the collection plate 106. For example, the imaging device 110 may capture images with different focal planes. The optical system 206 includes various lenses for magnification of the particles. The distances of the lenses are changed to adjust the focal plane. The various focal points may vary between, e.g., 2 -100 microns. A series of images of the collection plate 106 are obtained at different focal points. By combining images with various focal planes, the different sized particles may be imaged on the collection plate 106. An image processing device may use image layering techniques to achieve a wider focus plane. The optional illumination system 202 may include an array of LEDs in one or more different spectrums. The LEDs may include white LEDs, NIR / IR LEDs, and / or UV LEDs. Using different light combinations, the nature of particles (including, in addition to other data points, their shape) may be further differentiated. An image sensor 204 includes a CMOS camera. In another embodiment, the image sensor 204 and illumination system 202 may include fluorescence or spectroscopy techniques. As explained, airborne particle sensors are used in order to detect and measure particles in the air. These particles can include dust mites, pollen, animal dander, mould and other particulate contaminants. An airborne particle sensor can, optionally, be included within a sensing device such as that described with reference to Figure 2 of the present disclosure. One type of particle sensor uses a light source and a photodetector to detect the presence of particles based on the scattering of light by the particles. However, the accuracy of these particle sensors can be affected by variations in the direction of the light. Furthermore, optical interference is also a common challenge with airborne particle sensors. More specifically, the accuracy of these sensors can be affected by the direction of the light source, the angle of the detector and other factors that can cause uneven illumination of the sample. In addition, stray light may cause a type of optical interference and can be very challenging for airborne particle sensors. A sensing device as described with reference to Figure 2 of the present disclosure enables rapid identification of allergens. However, the accuracy and reliability of particle detection may be affected by optical interference. Therefore, particle detection may often have to be performed in a controlled environment in order to attempt to reduce impact of optical interference. As an example, fluorescent light may cause significant interference (even if the sensing device is covered) as even a small gap in the cover of the sensing device enables the light to seep through and cause optical interference. Furthermore, a cover over the sensing device may restrict airflow through the sensing device and therefore may prevent particles from depositing on the collection plate without external intervention (e.g. removal of the cover). Accordingly, for at least these reasons (in addition to the reasons discussed in the Background) an airborne particle sensor is provided in accordance with embodiments of the disclosure. Figure 4 illustrates an airborne particle sensor 4000 in accordance with embodiments of the disclosure. The airborne particle sensor 4000 comprises a detector 4002, a sample holder 4004 and a light diffuser 4006. The sample holder 4004 is configured to hold a sample of the airborne particle. The detector 4002 is configured to detect the sample of the airborne particle held by the sample holder. Furthermore, in the airborne particle sensor 4000, the sample holder 4004 and an optical path between the sample holder 4004 and the detector4002 are enclosed within the light diffuser 4006. In the examples of Figure 4 of the present disclosure (and also Figure 5 of the present disclosure, which is discussed in more detail below) the sample holder 4004 is considered to be enclosed in the light diffuser even when a surface of the light diffuser does not cover an upper surface of the slide. Even when the surface of the light diffuser does not cover the upper surface of the slide, the light emitted from the light diffuser is the dominant light source and limits the stray light interactions during detection. In operation, the light diffuser of the particle sensor 4000 diffuses the light from the light source in all directions, creating a more uniform illumination of the sample. The scattered light from the particles in the sample is then detected by the detector (which can be a photodetector). The airborne particle sensor 4000 enables improved accuracy and reliability of the detection of airborne particles. In particular, the configuration of the light diffuser within the airborne particle sensor allows for even illumination of the particles. Furthermore, the light diffuser may diffuse the light such that the effects of stray light and other optical interference can be overcome or suppressed and reduced. Consistent particle detection can then be provided for every environment in which the particle sensor is to be used. This enables the particles or pathogens to be accurately and reliably identified. Furthermore, the airborne particle sensor 4000 reduces colour variability arising from background light. For example, in an office setting (or other such environment) the particles may appear more white (owing to the type of light source used in these environments) while in homes, the particles may appear more yellow (as people typically use "warm" light sources (with a yellow hue) in their homes). However, by using the airborne particle sensor 4000, the impact of variations in the hue of the external light sources can be reduced, thus reducing colour variability in the particles. This enables the particles or pathogens to be accurately and reliably identified. In some examples, the airborne particle sensor 4000 may further include a housing (not shown in Figure 4). The detector 4002, sample holder 4004 and light diffuser 4006 may then be included within this housing. The use of a housing may further reduce the effect of stray light and other optical interference. That is, the housing may be configured to reduce a level of external light, from outside the airborne particle sensor, reaching the sample holder. Thus, use of an optional housing may further improve the accuracy and reliability of particle detection. Furthermore, in some examples, the airborne particle sensor 4000 may also include a light source. This will be described in more detail later. Further details of the airborne particle sensor 4000 will now be described. <Detector> As explained with reference to Figure 4 of the present disclosure, the airborne particle sensor 4000 comprises an detector 4002. Indeed, the detector is configured to detect particles held by the sample holder of the particle sensor 4000. The type of detector used within the airborne particle sensor is not particularly limited. However, it will be appreciated that the detector is configured to detect the sample of the airborne particle held by the sample holder. In examples, the detector may be a type of photodetector. In examples, the photodetector may be an imaging device configured to capture an image of the sample held by the sample holder. This enables the sample to be analysed in order that particles can be detected. In examples, the imaging device is thus configured to capture scattered light from the airborne particle held by the sample holder. As explained, the detector may be a photodetector (a sensor that can covert light into an electrical signal). Furthermore, in examples, the photodetector may comprise a photodiode or a microelectromechanical system (MEMS). Alternatively, a metal-semiconductor-metal (MSM) photodetector can be used as the detector 4002 of the present disclosure. In some examples, the detector 4002 may be an image sensor 204 as described with reference to Figure 3 of the present disclosure. Therefore, the detector4002 may comprise a CMOS sensor (or CMOS camera). Therefore, it will be appreciated that the type of detector 4002 used within the airborne particle sensor 4000 is not particularly limited. Indeed, any type of detector can be used in accordance with embodiments of the disclosure provided that the detector can be configured to detect the sample of the airborne particle held by the sample holder (e.g. by capturing an image of the sample of the airborne particle). Advantageously, there is an even (uniform) illumination of the particle held by the sample holder 4004. This is because the sampler holder is enclosed within the light diffuser 4006 of the particle sensor 4000. Furthermore, the optical path between the sample holder and the detector 4002 is also enclosed within the light diffuser 4006. Thus, the stray light and other optical interference does not affect the detector 4002. That is, the detector 4002 may receive the light which has been scattered by the particles held by the sample holder enclosed within the light diffuser 4006. This enables the detector 4002 to obtain a more accurate and reliable image of the particles held by the sampler holder. In examples, the entirety of the detector does not need to be enclosed by the light diffuser, provided that the optical path between the sample holder 4004 and the detector 4002 is enclosed within the light diffuser. Furthermore, in examples, the entirety of the sample holder does not need to be enclosed by the light diffuser, provided that the optical path between the sample holder and the detector is enclosed within the light diffuser. The optical path is the path along which the scattered light travels between the particles held by the sample holder and the detector 4002. In the example of Figure 4, the optical path is shown as a direct line between the particles held by the sample holder. However, the present disclosure is not particularly limited in this regard. In examples, the optical path (also referred to as the optical pathway) between the sample holder and the detector 4002 can be more complex than the optical path illustrated in Figure 4. In particular, the optical path can include one or more additional optical elements to direct the scattered light from the sample holder 4004 to the detector 4002. Indeed, the optical path may optionally include at least one additional optical element from a list of: a lens, an optical filter, a window, a flat, a prism, a reflective component, a film or the like. A combination of these elements may also be included as part of the optical path. The use of one or more additional elements within the optical path can be changed in accordance with a desired location of the detector 4002 within the particle sensor 4000 relative to the sample holder. For example, one or more reflective elements may be included along the optical path in order to change the shape of the optical path in order that light from the sample holder reaches the detector 4002 at a given location in the particle sensor 4000. Furthermore, the use of one or more additional elements within the optical path can further improve the accuracy and reliability of the particle detector. For example, an optical filter may be provided in order to filter the light reaching the detector 4002. Alternatively or in addition, a lens (or other type of optical element) may be provided in order to focus scattered light on the detector 4002. In some examples, the particle sensor 4000 and / or the detector 4002 of the particle sensor 4000 can be controlled or controllable by an apparatus such as apparatus 1000 described with reference to Figure 1 of the present disclosure. In other examples, such as when the particle sensor is included within a sensing device as described with reference to Figure 2 of the present disclosure, the particle sensor 4000 and / or the detector of 4002 of the particle sensor may be controlled or controllable by circuitry of the sensing device. Further alternatively, one or more of the particle sensor 4000 and / or the detector 4002 of the present disclosure can be controlled or controllable by a server. <Sample Holder> As explained with reference to Figure 4 of the present disclosure, the airborne particle sensor 4000 comprises a sampler holder 4004. The sample holder 4004 is configured to hold a sample of the airborne particle. In a particle detector (such as particle detector 4000 of the present disclosure) the sample holder 4004 holds the sample of particles which are to be detected. The type of particle which is held by the sample holder is not particularly limited. However, typical airborne particles include particles such as dust mites, pollen, animal dander, mould and other particulate contaminants. Light then scatters off the particles held by the sample holder and is detected by the detector 4002. The type of sample holder used within the particle sensor 4000 is not particularly limited and can vary depending upon the situation to which the embodiments of the disclosure are applied. For example, the sample holder can be any type of holder that can hold the sample in the path of the light such that scattered light from the particles reaches the detector 4002. Therefore, the type of sample holder is not particularly limited. In some examples, the sample holder can include a filter, a lens or a slide. The particles to be detected are then held in the filter, lens or slide in order that they can be detected. In examples, the airborne particle sensor 4000 can be used within a sensing device such as the sensing device described with reference to Figure 2 of the present disclosure. In such an example, the sample holder may be a collection plate 106 as described with reference to Figure 2 of the present disclosure. When a collection plate 106 is used as a sample holder 4004 of the present disclosure, airborne particles may land naturally over time on the collection plate 106, or the airborne particles may be directed to the collection plate 106. For example, particles may deposit on the collection plate 106 under the effect of gravity. Alternatively, for example, the airborne particles may be directed to the collection plate 106 using the fan 104 to push or pull air flow to the collection plate 106. In some embodiments, the collection plate 106 may have a positive charge to attract particles. The particles collected on the collection plate can then be detected by the detector 4002 of the particle sensor 4000. In other examples, such as when a slide is used as the sample holder, a slide of particles to be detected may be placed within the particle detector for detection. cLight Diffuser> Furthermore, as explained with reference to Figure 4 of the present disclosure, the particle sensor 4000 further comprises a light diffuser (or light guide). The sample holder 4004 and an optical path between the sample holder 4004 and the detector4002 are enclosed within the light diffuser 4006. The configuration of the light diffuser within the airborne particle sensor allows for even illumination of the particles. This ensures that the effects of stray light and other optical interference can be overcome. More specifically, the light diffuser diffuses light across the sample held by the sample holder. Thus, the light diffuser enables an even distribution of light across the sample (global illumination of the particles) and reduces stray light interference or artefacts arising from an uneven distribution of light across the sample. The material used to construct the light diffuser is not particularly limited. In some examples, the light diffuser may be made of a translucent material. A translucent material may be used when a light source illuminating the sample is external to the light diffuser. In examples, the translucent material may be a plastic material. Alternatively, the translucent material may be a glass material. The present disclosure is not particularly limited in this regard and the diffuser can be made of a variety of different materials as required. In examples, a reflective coating may be provided on the light diffuser. This may be advantageous when it is desired to reduce the amount of light external to the light diffuser reaching the sample. The configuration of the light diffuser is not particularly limited, provided that the sample holder 4004 and an optical path between the sample holder 4004 and the detector 4002 are enclosed within the light diffuser 4006. This enables light to be evenly distributed across the sample regardless of the direction of the light source or the angle of the detector. In particular, it will be appreciated that the light diffuser can have a variety of different shapes and a variety of different sizes depending on the situation to which the embodiments of the disclosure are applied. For example, the size and shape of the light diffuser may vary in accordance with the size of the sample holder 4004 and the size of the detector 4002 used in the particle sensor 4000. Consider now Figure 5 of the present disclosure. Figure 5 of the present disclosure illustrates a light diffuser in accordance with embodiments of the disclosure. In this example, the sample holder 4004 is implemented as a slide. The slide thus holds the particle (or particles) to be detected by the particle sensor 4000. The optical pathway is enclosed within the light diffuser. The light diffuser of this example is configured to evenly distribute the light across the sample, regardless of a direction of the light source or the angle of the detector. In this specific example shown in Figure 5 of the present disclosure, the light diffuser is a pyramidal frustum. However, the light diffuser can have a variety of shapes and sizes to optimize the distribution of light on the sample (depending on factors including the shape of the sample holder and / or the shape of the detector). Indeed, in examples, the light guide may have any prism shape (including triangular, rectangular, hexagonal, heptagonal, octagonal and trapezoidal prisms). A pyramidal frustum is an example of a trapezoidal prism. The light diffuser as shown in Figure 5 can be made of a variety of materials, such as plastic or glass. However, the present disclosure is not particularly limited to these specific examples and any suitable translucent material can be used. Consider, now, Figure 6 of the present disclosure. Figure 6 illustrates a light diffuser in accordance with embodiments of the disclosure. In this example, a number of copies of the light diffuser having the shape of a pyramidal frustum are shown. Each of these light diffusers can individually be used within a particle sensor 4000 of the present disclosure. Furthermore, these light diffusers provide an example where the light diffuser being constructed from a translucent plastic material. Furthermore, optionally, the pyramidal frustum of the light diffuser can be coated with a reflective material, such as aluminium or silver, to further enhance the diffusion of light. Furthermore, this may be advantageous when it is desired to reduce the amount of light external to the light diffuser reaching the sample. Thus, the light diffuser 4006 of the particle sensor 4000 is configured to diffuse the light across the sample in a uniform manner. <Light Source> The particle sensor 4000 illustrated with respect to Figure 4 of the present disclosure comprises an detector, a sample holder and a light diffuser. However, in some examples, the particle sensor 4000 may further comprise a light source. That is, in some embodiments of the disclosure the light diffused by the light diffuser can originate from a location external to the particle sensor 4000. In other examples, the particle sensor 4000 may further comprise a light source. In this case, the light diffuser 4006 is then configured to diffuse the light from the light source across the sample holder. Accordingly, in accordance with embodiments of the disclosure, an airborne particle sensor for a sensing device is provided, the airborne particle sensor comprising: an detector, a sample holder and a light diffuser; wherein the sample holder is configured to hold a sample of the airborne particle; the detector is configured to detect the sample of the airborne particle held by the sample holder; wherein the sample holder and an optical path between the sample holder and the detector are enclosed within the light diffuser; and wherein the particle sensor further comprises a light source and wherein the light diffuser is configured to diffuse the light from the light source across the sample holder. Consider, now, Figure 7 of the present disclosure. Figure 7 illustrates a particle sensor in accordance with embodiments of the disclosure. In this example, the particle sensor further comprises a light source 4008. The light source is part of the particle sensor and is external to the light diffuser 4006. That is, the light from the light source must pass through the light diffuser in order to reach the sample container 4004. Accordingly, the light diffuser 4006 is configured to diffuse the light from the light source in order that the sample is illuminated by the light from the light source 4008 in a uniform manner. Furthermore, in this example (as illustrated with respect to Figure 7 of the present disclosure) the light source is contained within a structure of the light diffuser. That is, while the light source 4008 is external to the light diffuser (i.e. it is not inside the enclosed area containing the sample container and the optical path) it is contained within a structure of the light diffuser. This enables the form factor of the particle sensor to be reduced. In some examples, the structure may be a recessed section on the exterior surface of the light diffuser. Return now to the example of Figure 5 of the present disclosure. Figure 5 illustrates a top view of a light diffuser and a bottom view of light diffuser in accordance with embodiments of the disclosure. In this example, the bottom of the light diffuser comprises light source encasings in which the light source can be encased by the light diffuser. These light source encasings (as illustrated with respect to Figure 5 of the present disclosure) provide an example of a structure of the light diffuser within which the light source can be contained. Therefore, in this example, the light diffuser is arranged between the light source and the sample holder (with the light diffuser being arranged above (or on top) of the light source)). Furthermore, the light diffuser is configured such that it surrounds the sample holder (i.e. such that the sample holder and an optical path between the sample holder and the detector are enclosed within the light diffuser). Thus, in this example, the light diffuser is positioned above the light source and around the sample and is thus configured to evenly distribute the light across the sample regardless of the direction of the light source or the angle of the detector. That is, light from the light source must pass through the light diffuser in order to reach the sample held by the sample holder. Accordingly, the light diffuser is configured to diffuse the light from the light source in order to provide uniform illumination of the sample held by the sample holder. As previously explained, the accuracy of sensors (such as the detector4002) used to detect particles held by the sample container can be affected by the direction of the light source, the angle of the detector and other factors that can cause uneven illumination of the sample. However, according to embodiments of the disclosure, uniform illumination of the sample held by the sample holder can be provided. Therefore, the accuracy and reliability with which the particles held by the sample container can be detected can be improved. It will be appreciated that the present disclosure is not particularly limited to the example configuration illustrated with respect to Figure 5 of the present disclosure. For example, in this Figure the light source is contained within light source encasings in the exterior surface of the light diffuser. However, more generally, the light source, light diffuser and sample holder of the particle sensor may be configured in order that the light diffuser is arranged between the light source and the sample holder. Thus, the light from the light source must pass through the light diffuser in order to reach the sample held by the sample holder. Consider now Figure 8 of the present disclosure. Figure 8 of the present disclosure illustrates a particle sensor in accordance with embodiments of the disclosure. In this example, the particle sensor 4000 further comprises a light source 4008. However, in contrast to the example illustrated in Figure 7 of the present disclosure, the light source 4008 is not contained within a structure of the light diffuser. That is, in this example, the light source 4008 is arranged within the particle sensor 4000 by is separate from the light diffuser 4006. This can make it easier to construct the particle sensor 4000. However, similar to Figure 7 of the present disclosure, the light source is arranged externally to the enclosure which encloses the sample holder 4004 and the optical path. This means that light from the light source 4008 must pass through the light diffuser 4006 in order to reach the sample (as the light diffuser 4006 is arranged between the light source 4002 and the sample holder 4004). Thus, the light diffuser 4006 is configured to evenly distribute the light from the light source across the sample holder. Therefore, the accuracy and reliability with which the particles held by the sample container can be detected can be improved. Furthermore, it will be appreciated that while the particle sensor 4000 with a single light source has been described, the present disclosure is not particularly limited in this regard. That is, in embodiments of the disclosure, a plurality of light sources can be provided within the particle sensor 4000. Furthermore, in embodiments of the disclosure, the plurality of light sources can be arranged at different locations within the airborne particle sensor. Different light sources can be used in order to detect different types of particles. For example, visible light can be used for detection of pollen, while UV light can be used for detection of mould. Furthermore, the use of a plurality of a plurality of light sources may further improve the uniformity of the illumination of the sample. That is, while the light diffuser is configured to diffuse the light from the light source to provide uniform illumination of the sample held by the sample holder, the efficiency of the light diffuser at diffusing the light across the sample may be further improved when a plurality of light sources arranged at different locations within the airborne particle sensor are provided. This is because the light from the light sources will then reach the light diffuser from a plurality of different locations (instead of originating from a single point source). Thus, by using a plurality of light sources arranged at different locations within the airborne particle sensor, the uniformity of illumination of the sample may be further improved (which thus enables the accuracy and reliability of the particle sensor to be further improved). Consider again the example illustrated with respect to Figure 5 of the present disclosure. In this example, the bottom of the light diffuser can contain a plurality of light source encasings. A plurality of light sources can then be provided in the plurality of light source encasings. This provides an example of a particle sensor comprising a plurality of light sources wherein the plurality of light sources are arranged at different locations within the airborne particle sensor. In some examples, the plurality of light sources can be a same type of light source. In these examples, each light source may then illuminate the sample with a same type of light (i.e. light of the same wavelength range). However, in other examples, one or more of the plurality of light sources may be of a different type. This enables light of different types (i.e. light of a different wavelength range) to be used to illuminate the sample. This may be advantageous for further increasing the accuracy and reliability of the particle sensor, as different types of particles may be more accurately detected when using a particle wavelength range of light. In this regard, it will be appreciated that the type of light source is not particularly limited in accordance with embodiments of the disclosure. However, in some examples, the light source may be configured to emit at least one of visible light, ultraviolet (UV) light and / or near-infrared light. In examples, visible light may include light of a wavelength range 380-800nm, while near-infrared light may include light of a wavelength from 800 to 2500nm. UV light may include a wavelength range of 100 to 400nm. However, the present disclosure is not particularly limited in this regard and a different wavelength range may be produced by the light source depending on the situation to which the embodiments of the disclosure are applied (which may include, for example, the type of particle which is to be detected). In some examples, the light source may include at least one light-emitting diode. In other examples, the light source may include at least one laser. The use of a light-emitting diode or a laser may enable very specific control of the illumination of the sample to be provided. However, the present disclosure is not particularly limited to these specific examples of the light source and any suitable light source may be provided as required. <Advantageous Technical Effects> In accordance with embodiments of the disclosure, more accurate and reliable detection of particles when using an airborne particle sensor can be provided. In particular, the particle sensor of the present disclosure comprises a detector, a sample holder and a light diffuser; wherein the sample holder is configured to hold a sample of the airborne particle; the detector is configured to detect the sample of the airborne particle held by the sample holder; wherein the sample holder and an optical path between the sample holder and the detector are enclosed within the light diffuser. The present disclosure thus provides a particle sensor with a light diffuser that improves the accuracy and consistency of the particle detection. That is, the light diffuser allows for even illumination of the particles and overcomes problems related to stray light and other optical interference. Consider now Figure 9 of the present disclosure. Figure 9 illustrates an example of particle detection in accordance with embodiments of the disclosure. In the example of Figure 9, two images are provided. The first image (image A) on the left-hand side of Figure 9 illustrates an example image of particles detected by a particle detector which does not include the light diffuser of the present disclosure. The second image (image B) on the right-hand side of Figure 9 illustrates an example image of particles detected by a particle detector in accordance with embodiments of the disclosure. As can be seen, the effect of stray light and optical interference is reduced in panel B compared to panel A. In particular, the distinct pink colour of the analysis on panel A is due to unwanted wavelengths "polluting" the reading. As such, while particles can still be seen, it is difficult to obtain consistent readings in different environments. On the other hand, the example of panel B shows that the effect of the unwanted wavelengths "polluting" the reading is reduced, thus enabling consistent readings in different environments to be obtained. Accordingly, improved accuracy and reliability of particle detection can be achieved. It will be appreciated that the present disclosure is not particularly limited to these advantageous technical effects. Other advantageous technical effects are provided as will be apparent to the skilled person when reading the disclosure. <Clauses> In addition, embodiments of the present disclosure can be arranged in accordance with the following numbered clauses: 1. An airborne particle sensor for a sensing device, the airborne particle sensor comprising: a detector, a sample holder and a light diffuser; wherein the sample holder is configured to hold a sample of the airborne particle; the detector is configured to detect the sample of the airborne particle held by the sample holder; and wherein the sample holder and an optical path between the sample holder and the detector are enclosed within the light diffuser. 2. The airborne particle sensor according to clause 1, wherein the light diffuser is a prism. 3. The airborne particle sensor according to clause 2, wherein the prism is a pyramidal frustum. 4. The airborne particle sensor according to any of clauses 1 to 3, wherein the light diffuser is coated with a reflective material. 5. The airborne particle sensor according to any of clauses 1 to 4, wherein the light diffuser is made of a translucent material. 6. The airborne particle sensor according to clause 5, wherein the translucent material is plastic or glass. 7. The airborne particle sensor according to any of clauses 1 to 6, wherein the light diffuser is configured to diffuse light across the sample holder. 8. The airborne particle sensor according to any of clauses 1 to 7, further comprising a housing, wherein the detector, the sample holder and the light diffuser are contained within the housing. 9. The airborne particle sensor according to clause 8, wherein the housing is configured to reduce a level of external light, from outside the airborne particle sensor, reaching the sample holder. 10. The airborne particle sensor according to any of clauses 1 to 9, further comprising a light source and wherein the light diffuser is configured to diffuse the light from the light source across the sample holder. 11. The airborne particle sensor according to clause 10, wherein the light source is contained within a structure of the light diffuser. 12. The airborne particle sensor according to clause 11, wherein the structure is a recessed section on an exterior surface of the light diffuser. 13. The airborne particle sensor according to clause 10, wherein the light diffuser is arranged between the light source and the sample holder. 14. The airborne particle sensor according to any of clauses 10 to 13, wherein the light diffuser is configured to evenly distribute the light from the light source across the sample holder. 15. The airborne particle sensor according to any of clauses 10 to 14, wherein the light source is configured to emit visible light, ultraviolet and / or near-infrared light. 16. The airborne particle sensor according to any of clauses 10 to 15, wherein the light source comprises at least one light-emitting diode. 17. The airborne particle sensor according to any of clauses 10 to 16, wherein the light source comprises at least one laser. 18. The airborne particle sensor according to any of clauses 1 to 17, wherein the airborne particle sensor comprises a plurality of light sources. 19. The airborne particle sensor according to clause 18, wherein the plurality of light sources are arranged at different locations within the airborne particle sensor. 20. The airborne particle sensor according to any of clauses 1 to 19, wherein the detector captures scattered light from the airborne particle held by the sample holder. 21. The airborne particle sensor according to any of clauses 1 to 20, wherein the sample holder is a filter or a transparent slide. 22. The airborne particle sensor according to any of clauses 1 to 21, wherein the detector is a photodetector. 23. The airborne particle sensor according to clause 22, wherein the photodetector is a photodiode or a micro-electromechanical system, MEMS. 24. A sensing device comprising an airborne particle sensor according to any of clauses 1 to 23. Numerous modifications and variations of the present disclosure are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the disclosure may be practiced otherwise than as specifically described herein. In so far as embodiments of the disclosure have been described as being implemented, at least in part, by software-controlled data processing apparatus, it will be appreciated that a non-transitory machine-readable medium carrying such software, such as an optical disk, a magnetic disk, semiconductor memory or the like, is also considered to represent an embodiment of the present disclosure. It will be appreciated that the above description for clarity has described embodiments with reference to different functional units, circuitry and / or processors. However, it will be apparent that any suitable distribution of functionality between different functional units, circuitry and / or processors may be used without detracting from the embodiments. Described embodiments may be implemented in any suitable form including hardware, software, firmware or any combination of these. Described embodiments may optionally be implemented at least partly as computer software running on one or more data processors and / or digital signal processors. The elements and components of any embodiment may be physically, functionally and logically implemented in any suitable way. Indeed the functionality may be implemented in a single unit, in a plurality of units or as part of other functional units. As such, the disclosed embodiments may be implemented in a single unit or may be physically and functionally distributed between different units, circuitry and / or processors. Although the present disclosure has been described in connection with some embodiments, it is not intended to be limited to the specific form set forth herein. Additionally, although a feature may appear to be described in connection with particular embodiments, one skilled in the art would recognize that various features of the described embodiments may be combined in any manner suitable to implement the technique.

Claims

1) An airborne particle sensor for a sensing device, the airborne particle sensor comprising:a detector, a sample holder and a light diffuser;wherein the sample holder is configured to hold a sample of the airborne particle;the detector is configured detect the sample of the airborne particle held by the sample holder; andwherein the sample holder and an optical path between the sample holder and the detector are enclosed within the light diffuser.2) The airborne particle sensor according to claim 1, wherein the light diffuser is a prism.3) The airborne particle sensor according to claim 2, wherein prism is a pyramidal frustum.4) The airborne particle sensor according to any of claims 1 to 3, wherein the light diffuser iscoated with a reflective material.5) The airborne particle sensor according to any of claims 1 to 4, wherein the light diffuser is made of a translucent material.6) The airborne particle sensor according to claim 5, wherein the translucent material is plastic or glass.7) The airborne particle sensor according to any of claims 1 to 6, wherein the light diffuser is configured to diffuse light across the sample holder.8) The airborne particle sensor according to any of claims 1 to 7, further comprising a housing, wherein the detector, the sample holder and the light diffuser are contained within the housing.9) The airborne particle sensor according to claim 8, wherein the housing is configured to reduce a level of external light, from outside the airborne particle sensor, reaching the sample holder.10) The airborne particle sensor according to any of claims 1 to 9, further comprising a light source and wherein the light diffuser is configured to diffuse the light from the light source across the sample holder.11) The airborne particle sensor according to claim 10, wherein the light source is contained within a structure of the light diffuser.12) The airborne particle sensor according to claim 11, wherein the structure is a recessed section on an exterior surface of the light diffuser.13) The airborne particle sensor according to claim 10, wherein the light diffuser is arranged between the light source and the sample holder.14) The airborne particle sensor according to any of claims 10 to 13, wherein the light diffuser is configured to evenly distribute the light from the light source across the sample holder.15) The airborne particle sensor according to any of claims 10 to 14, wherein the light source is configured to emit visible light, ultraviolet and / or near-infrared light.16) The airborne particle sensor according to any of claims 10 to 15, wherein the light source comprises at least one light-emitting diode.17) The airborne particle sensor according to any of claims 10 to 16, wherein the light source comprises at least one laser.18) The airborne particle sensor according to any of claims 1 to 17, wherein the airborne particle sensor comprises a plurality of light sources.19) The airborne particle sensor according to claim 18, wherein the plurality of light sources are arranged at different locations within the airborne particle sensor.20) The airborne particle sensor according to any of claims 1 to 19, wherein the detector captures scattered light from the airborne particle held by the sample holder.21) The airborne particle sensor according to any of claims 1 to 20, wherein the sample holder is a filter or a transparent slide.22) The airborne particle sensor according to any of claims 1 to 21, wherein the detector is a photodetector.23) The airborne particle sensor according to claim 22, wherein the photodetector is a photodiode or a micro-electromechanical system, MEMS.24) A sensing device comprising an airborne particle sensor according to any of claims 1 to 23.

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