The present invention relates to the identification of airborne particles and, more specifically, to systems and techniques to address condensation.
There remains a need in agriculture to physically detect airborne pathogens before infestation enabling preventative action. Being able to capture, inspect, classify, and alert growers of the presence of harmful airborne pathogen spores allows growers to take preventative actions, optimize pest management practices, and minimize yield losses.
Monitoring of pathogen spores is also of interest during produce transportation and storage, such as in large indoor storage facilities where apples may be kept for many months.
There are many other applications for airborne particle monitors. For human health, it is of interest to monitor airborne allergens such as pollen and mold spores. Detection of airborne pathogens that effect the health of pets, livestock and other animals may also be of interest. Further applications for monitoring of airborne particles, not necessarily pathogens, may develop in the future.
One challenge, however, in identifying airborne particles is the presence of condensation. The condensation can make it difficult to identify a particle as being a pathogen spore. Condensation may also lead to undesirable corrosion.
In an embodiment, condensation associated with the collection and identification of airborne particles is detected. Upon the detection, one or more condensation countermeasures are triggered to address the condensation.
These components work together to draw in or sample ambient air 130, collect particles that may be present in the air, direct light or radiation into the collected particles, capture one or more images of the collected particles, and analyze the images in order to identify the particle. In an embodiment, the identification and classification of particles is based on image recognition and spectral analysis techniques. The particles are optically probed by being subjected to certain lighting or radiation conditions. Images are then taken of the particles. Analysis of the images includes examining how different wavelengths or colors of light (which may include ultraviolet light) are absorbed, reflected, or scattered according to the images. A detailed discussion of collection and analysis techniques is provided in U.S. patent application Ser. No. 15/178,170, filed Jun. 9, 2016, now U.S. Pat. No. 9,933,351, issued Apr. 3, 2018; U.S. patent application Ser. No. 15/667,829, filed Aug. 3, 2017, now U.S. Pat. No. 10,458,990, issued Oct. 29, 2019; and U.S. patent application Ser. No. 15/895,431, filed Feb. 13, 2018, now U.S. Pat. No. 10,684,209, issued Jun. 16, 2020. These patents are assigned to the same assignee as this patent application and are incorporated by reference along with all other references cited.
The condensation countermeasures include processes, hardware components, or both to address condensation that may be present in the ambient air to facilitate an accurate identification of the airborne particles.
Condensation Conditions
As a specific concrete example, imagine that during the day the temperature reaches a high of 25° C. and a relative humidity (RH) of 65%, and then late at night the temperature drops to 10° C. If the absolute water content of the air were to remain the same (at a vapor pressure of 2 kPa), the relative humidity at 10° C. would increase to 150%. Such super-saturation is not stable and results in water condensation.
We may experience such water condensation as dew, such as water condensing on blades of grass. We may also experience such water condensation as fog, where water droplets form in the air. These are examples where condensation occurs in the ambient environment due to a drop in temperature.
Condensation may also occur when ambient air is saturated or close to saturation, and the airborne particle device is colder than ambient air. Sampled ambient air is cooled when entering the device, possibly leading to condensation. This scenario might occur in a greenhouse when the morning sun warms up and humidifies the greenhouse air faster than it heats up the particle monitoring device.
Condensation conditions may also be encountered in airborne particle detector applications outside of agriculture. For example, consider an airborne particle monitor being used to monitor mold spores during mold remediation after repair of a leaking water pipe. Wet items from the leak may saturate the air leading to condensation when the temperature drops at night.
Problems Caused by Condensation
Water condensation can negatively affect the performance of an airborne particle detector in two ways. The creation of water droplets may be a problem via increasing the number background particles, thus complicating recognition and analysis of the particles of interest. This is conceptually illustrated in
Water that condenses on particles of interest may be another problem. The optical signatures of particles of interest may well change due to water condensation. If water condensing on a particle of interest is absorbed by the particle, the moistened particle may well swell and change shape and other optical characteristics. (An analogy here is that a dried prune looks different after being stewed in water.) If instead, or in addition, condensed water forms a water film on a particle of interest, the water film may also modify the particle's optical signatures. Such a water film is also referred to as a capillary layer.
These issues with water condensation on particles of interest are illustrated in the conceptual sketches shown in
Independent of its effects on spore image quality, in some applications condensation may also be undesirable for an entirely different reason, namely, corrosion. This may be of particular concern in applications, such as apple cold storage, which use air enriched in carbon dioxide (CO2). When carbon dioxide diffuses into water drops, carbonic acid (H2CO3) is formed, potentially leading to undesired corrosion of susceptible components and materials. For example, electronics and copper wiring may be susceptible to acidic water droplets. Such susceptible components and materials may be coated or embedded with protective materials such as silicone potting compound. Alternatively, or in addition, condensation of acidic water droplets can be avoided using condensation countermeasure methods described further below in this document.
Droplets From Other Sources
There can be droplets from other sources. As noted above, one possible problem associated with condensation is an increased number of background particles. Some countermeasures for an increased number of background particles may be effective for other causes of increased numbers of background particles, such as agricultural spraying.
The detector includes a housing 710 that contains most of the device components. The housing is rotatably connected to a base 720. The housing includes an opening that may be referred to as an air-intake slot 730 and a cartridge door 740 next to the air-intake slot. The air-intake slot forms a funnel-like shape as it penetrates the thickness of the housing. The cartridge door opens to allow for the insertion and removal of a media cartridge within which particles in the ambient air are collected.
Specifically, opening 925A corresponds to the particle collection zone. When the cartridge is loaded into the detector, the cartridge is positioned so that the particle collection zone is next to the air-intake slot and thus facing a flow of ambient air being drawn into the detector. Airborne particles present in the air are trapped by the adhesive coated tape. The air exhausts out from the cartridge through opening 925C. The portion of the tape at the particle collection zone and having the trapped particles can be advanced to the particle inspection zone. There is an illumination and optical assembly above the particle inspection zone. The illumination assembly may include multiple light sources such as multiple light emitting diodes (LEDs). The light sources may be arranged at different positions about the inspection zone. A light source may emit light that is different from or the same as light emitted by another light source. The optical assembly may include a camera sensor and lens. Opening 925B at the particle inspection zone allows light from the illumination assembly to be directed at the trapped particles and images to be captured by the optical assembly.
Hardware Components To Reduce Or Eliminate Condensation—Heating
The blower creates a vacuum to draw ambient air through the detector. Arrows 1030A-C indicate a direction of air flow through the detector. Air passes through the air-intake slot, to the particle collection zone, through the cartridge, and out the detector through an exhaust 1035.
In an embodiment, to reduce, avoid, or eliminate condensation, the relative humidity (RH) is brought below 100%. This can be done either by increasing the temperature, e.g., by heating, or by removing water vapor from the air, e.g., by desiccation, or both. Let us first consider heating.
The heater, indicated by a resistor symbol, is included to raise the temperature inside the device relative to the ambient temperature outside the device. If the inside temperature is sufficiently elevated, the internal relative humidity drops below 100% even when external relative humidity is 100% or larger. This halts condensation and enables evaporation of existing droplets.
In
In some applications, electrical power for heaters may be provided. For example, in an indoor apple storage facility, power might be provided by electrical outlets. In other applications, carefully managing power consumption is more critical. For example, excessive power consumption by heaters is to be avoided for a device installation located in a corn field and having a self-contained solar panel and battery power supply.
In an embodiment, heating of a lower portion of the device is made difficult by the constant flow of ambient air (e.g., 1030A) through the air intake slot, past the particle collection zone, through the cartridge as indicated by internal air arrow 1030B, and on through the blower to the exhaust. It may be sufficient that the desired elevated temperature is provided in the vicinity of the particle inspection zone. This sufficient condition may be met, for example, if energy delivered to the heater is sufficient to warm the detector above a “warm air boundary” as indicated by a broken line 1040, even if below the boundary the air is not warmed enough to avoid condensation.
For applications with concerns regarding corrosion due to condensation of (acidic) water droplets, it is preferable to place corrosion sensitive components above the warm air boundary 1040. For example, as shown in
Addition of thermal insulation, such as a layer of foam, foil, or both to the inside of at least a portion of housing 710 may reduce the amount of energy that needs to be provided to heater 1020 to maintain a desired temperature differential. In some cases, heat generated by motherboard 1005 may be sufficient, eliminating the need for a separate heating element.
Additional air baffles may be added to further segregate the unheated air below the boundary from the heated volume above the boundary.
When ambient temperature and humidity is predictable and stable, such as inside an apple storage facility, the thermal design may be fine-tuned to efficiently suppress undesired condensation.
In particular, if corrosion due to water droplets is of little concern and the goal is to protect image quality, the energy demands of the heater may be reduced if it is strategically located where it is most needed.
The approach shown in
For example, in another embodiment, the local heater may be embedded in the optical platform. The local heater may be a resistor to which a voltage “V” is applied and a current “I” is passed. The electrical power, P=I2R=V2/R, consumed by the resistor is converted to heat. The resistor may be, for example, a standard axial resistor, a surface mount resistor, or a length of nichrome wire.
A local heater may be placed to directly heat the particle inspection zone. In some applications this is difficult to do without mechanical interference with other components such as the lens. The inventors have discovered that it may be advantageous to heat the particle inspection zone indirectly. The local heater may be placed to heat air that then flows through the particle inspection zone. That is, from the perspective of air flow, the local heater may be placed upstream of the particle inspection zone. An example design is illustrated in
Of particular interest for local heating of a particle inspection zone 1242 is air flow 1245 that follows the media tape path from the particle collection zone to the particle inspection zone, and then continues above and to the left of the take-up reel and exits the cartridge. See the air flow path indicated by three arrows 1235, 1240, and 1245, that last one of which is labeled “above air flow”.
As illustrated in
As shown in the example of
It is desirable that heat generated at such a resistor be directed toward the above air flow and away from the optical platform material. As illustrated in
The sketches shown in
In an embodiment, the optical platform is provided with an appropriately shaped and placed groove to receive such a sleeved-resistor local heater.
More particularly,
The heater insulating sleeve, as shown in the examples of
Compared to a global heater, a small carefully placed local heater greatly reduces power requirements. Reduced power means longer battery life and less expensive electronics. For example, the inventors calculate that if at least 50% of heat from the local heater goes into the air, and the above air flow rate is under one-half liter per minute, then 100 mW of electrical energy delivered to the local heater is sufficient to raise the air temperature by 5° C. This low power requirement avoids the need for special power electronics. Instead, it is sufficient to power the local heater with a few general-purpose input/output (GIO) pins of common microprocessors; for example two GIO pins of a Raspberry Pi. Impact on battery life can be further reduced or minimized by turning on the heater only when needed.
One method to determine when heating is truly needed (and hence reduce or minimize power consumption) is to process humidity (and temperature) measurements from sensors inside and/or outside the monitor housing. In addition, or instead, image processing software (perhaps using artificial intelligence) may be used to identify water droplets and turn on the heater when such negative effects due to condensation is observed in the optical data. It may not be necessary to thoroughly dry particles of interest in the particle inspection zone, it is sufficient to remove enough moisture so that good optical data may be collected.
Table A below shows spreadsheet calculation results for a few different choices of key inputs.
For any given application environment, the precise temperature increase required to avoid condensation may be determined from experiment. The values of flow rate and efficiency inputs are strongly influenced by engineering choices.
The power requirements scale with the air flow rate through the particle inspection zone. Power requirements may be reduced by reducing this flow rate. Methods for doing so are discussed below.
As shown in the example of
For a given application, the rate ambient air is sampled, Iintake is often specified. For example, it may be specified at 10 liters per minute and the pressure difference due to the blower, Vblower, engineered accordingly. The fraction of the sampled ambient air that passes through the particle inspection zone, Iabove, via the above air flow is determined by the following relationship.
The formula above tells us that for a fixed ambient air sampling rate, Iintake, the flow rate through the particle inspection zone, Iabove, may be reduced by either increasing resistance to above air flow, Rabove, or decreasing resistance to other air flows such as the around air flow resistance Raround.
Referring back now to
As noted above, Iabove can be reduced (thus reducing local heater power requirements) by decreasing Raround. Adding concave indents around the air intake slot is one way to do this.
Compare the two sketches shown in
The above discussion considers the case that the local heater is a resistor. In another embodiment, the particle collection zone may be heated with an infrared radiation source. For this purpose, an infrared illumination source may be added to the optical platform. For example, instead of illuminating the particle inspection zone with three white LEDs and an UV LED, it may be illuminated by three white LEDs, an UV LED, and an infrared illumination source. Before image capture, the infrared illumination source may evaporate any water droplets in the particle inspection zone as well as dry out any overly moistened particles of interest. The desired infrared illumination source is small in size and provides a well-directed beam of infrared “heat.”
Hardware Components To Reduce Or Eliminate Condensation—Desiccation
The detector shown in
Desiccating of a lower portion 2813 of the device may be rendered difficult by the constant flow of moist ambient air 2820 through an air-intake slot 2830, past the particle collection zone, through the cartridge as indicated by internal air arrow 2830, 2840 and on through a blower 2810 to an exhaust 1035. It may be sufficient that the desired reduced humidity is provided in the vicinity of the particle inspection zone. This sufficient condition may be met, for example, if the desiccator results in dry air above a “dry air boundary” 2842 indicated in
If periods of high ambient relative humidity are brief interruptions within much longer periods of lower relative humidity, saturation of the desiccator may be avoided. The longer periods of lower relative humidity may dry out the desiccator sufficiently to function through the next brief period of high relative humidity. If not, means may be provided to dry out the desiccator.
For example, a heating element may be provided (as shown above) to rapidly and temporarily heat and dry out the desiccator.
In another embodiment, the detector may include hydrophobic and hydrophilic surfaces. In some applications, it may be desirable for particle collection/inspection surfaces to be hydrophilic. This does not prevent condensation and may even increase it, but will encourage condensation to take the form of a more uniform film rather than isolated droplets. This may be less distracting for optical image processing. This is analogous to scuba divers applying hydrophilic coatings to the inside of diver masks to prevent them from fogging up; condensation still occurs, but in a thin film that does not affect visibility.
Hardware Components To Reduce Or Eliminate Condensation—Air Flow
If condensation is caused by the detector being at a lower temperature than ambient air, such as when greenhouse air warms in the morning sun faster than the detector, then increasing air flow may help the detector reach ambient temperature. Once the detector reaches ambient temperature, condensation is less likely.
Increasing air flow through the device (e.g., by increasing electrical power to the blower) increases heat transferred from ambient air to the device. Part of this is simple heat conduction from the warmer air to cooler parts of the device. This may be enhanced by the heating effects of condensation. The latent heat released as water vapor becomes condensed water also heats the device.
Increasing air flow may well temporarily increase condensation. By enabling the device to more quickly reach thermal equilibrium with ambient air, increased air flow shortens the time during which optical data is compromised by condensation effects. It is a bit like ripping off a band-aid quickly rather than slowly in order to get the pain over with sooner. For some applications, this may be a useful method for reducing down time due to condensation.
In an embodiment, a condensation mitigation strategy includes an increase of air flow speed on to a particle collection zone. If the monitor has a variable speed blower that pulls air and particles through the intake and into the capture or inspection zone, a signal can be sent by the processor to increase the fan or blower speed to therefore accelerate air flow through the system which leads to achieving a faster equilibrium of the system where temperatures balance between inside and outside the system. At first this may seem contradictive because more air flow will cause more condensation on the surface of the inspection zone, but at the same time it accelerates the internal system achieving temperatures outside of the condensation window. In the case of an initial large temperature difference between the monitor and humid ambient air for example, it accelerates thermal equilibrium of the system decreasing the likelihood of condensing drops forming on the inspection zone surface.
Processes To Recognize And Reject Water Droplets In Images
Water droplets on a surface tend to have an axis of rotational symmetry. (Synonyms for rotational symmetry are “cylindrical symmetry” and “axial symmetry”.) The axis of symmetry goes or passes through the center of the droplet and is perpendicular to the surface. If the surface is horizontal, then the axis of rotational symmetry is vertical. Due to surface tension, water droplets have smooth rounded surfaces with strong specular reflections. The rotationally symmetric smooth rounded shape of water droplets leads to distinctive optical signatures. These distinctive signatures be used to recognize and reject water droplets in the optical data of airborne particle detectors.
Let's first look at how these principles apply to optical data from a detector device having a lens-based microscope.
Light sources, such as first and second white LEDs 3020A,B are positioned about the particle inspection zone so as to illuminate the particle inspection zone or otherwise direct light to particles brought to the particle inspection zone. In an embodiment, white light LEDs illuminate the water drop as shown. Portions of the smooth rounded surface of the water droplet are at just the right orientation to reflect white LED light into the optical column. This reflection is specular, that is, mirror like.
Specular reflection of light 3120 from the three white LEDs appears as three small bright spots in the camera sensor images. Due to the water droplet's smooth rounded and rotationally symmetric shape, these specular reflections provide a distinctive signature.
As drawn in
In the above discussion, it is assumed that during image capture, all three white LEDs are activated, resulting in three specular reflection spots. Images may also be collected with illumination from two or only one white LED. Illumination with only one white LED will produce only one specular reflection spot, which is a less distinctive optical signature. For the purpose of recognizing (and rejecting) water droplets, it is preferable to capture images using two and more preferably three white LEDs. In an embodiment, an airborne particle detector includes more than three white LEDs thus providing water droplets with even more unique optical signatures. However, with three white LEDs, the optical signature of water droplets is already very distinctive and useful. If the illumination source forms a ring about the optical system axis, then the specular reflection will take the form of a circle.
To accentuate the optical signature of water droplets, illumination conditions may be changed. For example, one may take advantage of the brightness in camera sensor images of specular reflection spots on water droplets. By significantly reducing the illumination intensity of the white light LEDs of
Processes For Moist Spore Reference Library
A more subtle countermeasure involves the reference particle features used to recognize particles of interest. For example, for a given species of spore, the characteristics of a moist spore may be different than the characteristics of a dry spore. When no water droplets are present, the particle recognition software may use reference characteristics for dry spores while when many water droplets are seen in images, the particle recognition software may use instead reference characteristics for moist spores. Similar concepts apply to detection of dry or moist pollen grains, or any other type of particles of interest whose characteristics change with moisture. These concepts are explained further below.
Problems may arise if the particle reference library contains characteristics of dry particles while the image recognition engine is processing optical data for moist or wet particles. This can lead to false negatives in which, say, particles of type A are present but not recognized because water has changed their characteristics. This false negative problem may be addressed by having a particle reference library that includes both dry and wet characteristics of particles types of interest.
In some applications it may be desirable during moist conditions to remove the dry characteristics of particles from the particle reference library, or otherwise constrain the image recognition engine to use only wet characteristics. Eliminating unneeded characteristics from the particle reference library may reduce the rate of false positives.
The particle moisture state may be spilt into more categories than simply dry or wet. As shown in the example of
Referring again to
In an embodiment, the processor of the particle detector is communicatively coupled to storage within which the particle reference library is maintained. In an embodiment, the particle reference library is maintained on a storage device local to the particle detector. For example, the particle reference library may be stored on a nonvolatile storage device contained within the housing of the particle detector or attached as an accessory to the particle detector. Examples of nonvolatile storage include hard disk or solid-state storage (e.g., flash, or USB flash drive plugged into a USB port of the particle detector). In another embodiment, the particle reference library is maintained on a central storage system, remote from the particle detector. In this embodiment, the particle detector includes a network interface to connect the particle detector to the remote central storage system via a network. The network may include a local area network, wide area network, wireless network, the Internet, or any other suitable communication network.
The particle characteristics stored in a particle reference library, such as particle reference libraries 3215, 3405 and 3505 of
To capture three-dimensional images, referring to
The optical system may have one or more lenses. Alternatively, the optical system may be lens free. This possibility is discussed further below in connection with
Three-dimensional image data may be monochrome, or may contain standard RGB (red-green-blue) color information, or may contain richer color information that may be described as “multi-spectral” or “hyper-spectral”. Enhanced color information provides further data from which to extract particle characteristics for particle reference libraries.
Image data with enhanced color information and/or three-dimensional information may enable improved analysis of water droplets, moisture or condensation content. This may further support implementation of the condensation or moisture countermeasures described elsewhere in the document.
In brief, in a step 3605 a determination is made as to whether condensation is detected. If condensation is detected, in a step 3610 condensation countermeasures are activated. Condensation countermeasures may be maintained until no condensation is detected. For example, in a step 3615, another determination is made as to whether condensation is detected. If condensation is not detected, in a step 3620 condensation countermeasures are deactivated.
In an embodiment, the detection of water droplets in the camera sensor images triggers the heater (e.g., heater 1217,
In an embodiment, a method includes: collecting particles onto a tape media; advancing the tape media, including a section of the tape media having the particles, from a collection zone, past a heater, and to a particle inspection zone at which a first image of the particles is captured; detecting, from an analysis of the first image, that there are water droplets; rewinding the tape media, including the section of the tape media having the particles, to the heater; activating the heater for a threshold period of time; upon the threshold period of time being reached, deactivating the heater; advancing the tape media, including the section of the tape media having the particles, from the heater to the particle inspection zone; capturing a second image of the particles; analyzing the second image to determine whether any remaining water droplets can be detected; if there are water droplets detected, repeating the rewinding the tape media and activating the heater until there no remaining water droplets that can be detected; and if there are no remaining water droplets that can be detected, proceeding with an image analysis to identify the particles.
The above technique relies on image recognition or machine vision to detect the presence (or absence) of water droplets rather than climate sensors such as humidity sensors or temperature sensors. In an embodiment, such climate sensors can be omitted or excluded from the particle detector. Omitting such climate sensors can help to lower the overall cost of the particle detector and can facilitate a compact form factor.
In an embodiment, a method includes collecting particles from ambient air onto a section of tape media, the region of tape media being in a state having a first level of condensation; advancing the tape media, including the section of tape media having the particles, to a heater; activating the heater to reduce the first level of condensation to a second level of condensation, less than the first level of condensation; after the first level of condensation has been reduced to the second level of condensation, advancing the tape media, including the section of the tape media having the particles to a camera sensor; and capturing, via the camera sensor, an image of the particles while the particles are in a state having the second level of condensation.
In an embodiment, a method includes: activating a blower to draw, into a particle detector ambient air, and collect particles in the ambient air onto a tape media; advancing the tape media, including a section of the tape media having the particles, from a collection zone, past a heater, and to a particle inspection zone at which an image of the particles is captured; detecting, from an analysis of the image, that there are water droplets; activating the heater to warm a volume of air below the heater; and maintaining activation of the blower to draw the volume of warmed air to the particle inspection zone.
This flowchart can be extended for more than two humidity states, such as dry, non-condensing moist, and condensing. The decision diamond of this process, includes processes to determine if condensation is occurring, or more generally to know ambient humidity conditions. Below are some examples of techniques that may be used either individually or in combination.
1) Observation of water droplets in optical data
2) Humidity and temperature sensors placed in ambient environment
3) Weather data on the internet or ‘cloud’ (for outdoor applications)
4) Quality of matches with reference particle characteristics (e.g., if detected particles better match reference data for wet particles than for dry particles, use reference library for wet particles)
An embodiment may include other condensation detection techniques instead of or in addition to any of the techniques listed above. In an embodiment, information correlated with condensation may be collected via image sensing (camera), a combination scatter light and UV fluorescence sensing, sensing of droplet disruption of total internal reflection of near infra-red light per methods of automobile windshield rain sensors, sensing humidity with a capacitive humidity sensor, and combinations of these and others that have the ability to discriminate the presence of condensation water droplets or condensing conditions. Such sensors may be placed within the particle inspection zone or may be placed at or between the particle collection zone and the particle inspection zone. A variant may be that one or a combination of these are used outside of the monitor and, or, in the vicinity as long as it is representative of what the particle sensor is experiencing (has been calibrated, etc).
Modern developments in computer science may provide more sophisticated methods for adapting to the effects of moisture and condensation on particles of interest. Smart software intelligence (machine learning, artificial intelligence (AI), deep learning, and so forth) may enable classification schemes that incorporate pre-taught training sets of particles subject to various moisture and condensation conditions.
Modeling—Predictive Rather Than Reactive
In some applications, it may be useful to take action, such as turning on a local heater, before condensation occurs. This motivates the development of predictive models that anticipate when condensation may occur. Such a predictive model may utilize a variety of inputs including measurements from humidity sensors and thermometers, the time of day, weather predictions, any evidence, or lack thereof, of humidity affecting particles in captured images, schedules for the turning on of sprinklers or sprayers. Predictive models may utilize a variety of computational methods including artificial intelligence and machine learning. Mitigating measures in response to predictions of condensation may be any of the condensation countermeasures discussed above.
In an embodiment, condensation countermeasures include reducing the time between particle capture and particle imaging, thus reducing the time available for condensation to occur. In embodiments using a tape media cartridge, the rate that the tape is advanced may be accelerated so that particles collected at the particle collection zone arrive more quickly at the particle inspection zone. In other embodiments not using a removable cartridge, and instead using a non-removable substrate surface that is transported from a particle collection zone to a particle inspection zone, the transit time can again be accelerated in order to reduce the time available for condensation to occur. Even if condensation is not completely eliminated, less condensation may lead to more accurate classification of particles. Like with other condensation countermeasures discussed above, this accelerated transit from collection to inspection zones may be activated by an intelligent operating system using predictive modeling and input information from various sources
Beyond Condensation
Some of the countermeasures described above are not limited to water droplets due to condensation, but may also apply to other sources of droplets or moisture such as agricultural sprays such as fungicide sprays. That is, in an embodiment, similar detection and mitigation strategies when the source of the water droplets is not condensation but fungal sprays and other liquid or aerosol type of chemicals that may come in and interfere with what is otherwise considered normal or regular operation of the system and therefore calls for hardware mitigation strategies and or different machine learning (ML)/artificial intelligence (AI) techniques may be deployed.
In an embodiment, the presence of water droplets touching and/or fully covering particles to be inspected is taken into consideration. In this case the detection of droplets or “undesired foreign” aerosols may trigger a different optical inspection scheme such that a specific wavelength may see through water while another one collects an ideal particle signature. It may also be that a dry spore model is subtracted from optical images or optical fingerprints as long as the amount of water or “foreign substance” is measured and a subtraction is performed to accurately classify the particles. The data captured here may be used to send these data or signals to an outer intelligence that helps control the environment where the monitor device is present or assuming locations have the same ambient characteristics these can be controlled/changed/altered/edited in their machine controls/etc using this data towards controlling any parameters that lead to undesirable ambient characteristics such as condensation, operating within a pathogen growth conducive environment or to help monitor further locations where these is to be prevented. In an embodiment, the data can run on a digital platform informing a user or another form of intelligence autonomous or semi-autonomous (limited human user input, but could also be a different intelligence tasked with a different purpose that overlaps to analyze and provide an input to a data set).
In some embodiments, captured images, or more generally optical inspection data, are processed to subtract or otherwise compensate for the effects of water condensation before comparing to a particle reference library (such as particle reference library 3215 of
In some embodiments, mitigation measures may include altering illumination used during image capture. For example, consider a case where under combined white-light and UV illumination the images are unduly corrupted by specular reflections of visible light from capillary water films forming around particles of interest (e.g. pollen grains). It this case, it may be advantageous to capture fluorescence images resulting from UV illumination only. As water does not fluoresce under UV illumination, this eliminates the capillary water film, and water droplets, from captured images leaving only the image of the (fluorescing) particles of interest. In addition to modified illumination, under condensing conditions, it may also be desirable to modify the processing of captured images. For example, red pixel data may be removed if the desired fluorescence signal is blue or green. In brief, how images are captured may be a function of moisture conditions.
In some embodiments, countermeasures may go beyond just adapting to ambient environmental conditions that lead to condensation, but actually changing the ambient environment itself. For example, a greenhouse system may include control of sprinklers, heaters, air ventilation including windows and fans, etc. When condensation conditions occur, or appear imminent, one or more of these greenhouse system controls may be altered. Anything that reduces or eliminates condensation is a possible countermeasure.
In an embodiment, a detector device having condensation countermeasures may be particularly suited for greenhouse applications. In other embodiments, a detector device having condensation countermeasures also addresses needs for outdoor applications. Condensation may occur in outdoor/nature during a combination of rain and aided by hot winds. Hot winds subject to rain rapidly absorb water and become saturated. If such warm water saturated ambient air is drawn into a detector device whose interior is still cooler than ambient air, condensation will occur. Fog events are another circumstance when condensation within a detector device may be an issue. In brief, condensation countermeasures are relevant to both indoor and outdoor applications.
Here are some specific applications where condensation countermeasures are needed. Consider orchards, for example, in late summers in locations such as Napa, Calif. where the earth/soil gets very hot and rapidly evaporates moisture during the day. The temperature drops in the late afternoon and evening and continues dropping until the early morning sun rises and warms the canopy. As the temperature drops, a fog may form resulting in condensation conditions. Relevant applications are not limited to agriculture. For example, consider indoor mold remediation needed after a leaking water pipe is repaired. Again as temperature rises air absorbs moisture and then when temperatures drop condensation may occur. Other environments where suddenly surface condensation may occur are boiler rooms in industrial and transportation (cruise ships and large boats as examples) venues, kitchens, and near building entrances (doors and windows) with high pedestrian foot traffic (hotel entry/exit areas where doors and window may open and close). There are many applications where conditions are conducive to the condensation phenomena.
In some embodiments there is a monitor placed inside a vehicle. The vehicle may be autonomous and/or human operated. In certain circumstances, a monitor inside a vehicle may be subject to condensation. Particularly during cold winter days or hot summer days, the temperature of air within a vehicle can vary significantly as doors and windows open and close, and heaters or air conditioners are turned on and off. From time to time, the ambient air inside the vehicle may be considerably warmer than the interior of the monitor. Humidity conditions may also vary, such as when evaporation from snow covered or rain-soaked clothing dry out. When the ambient air inside the vehicle has high relative humidity and has a temperature exceeding the interior of the monitor, undesired condensation may well occur. Condensation countermeasures are of interest in applications in which monitors are placed inside vehicles.
Different particles of interest may react differently to condensation conditions. Water condensed on pollens tend to form a capillary layer. In contrast water condensing on fungal spores are more likely to be absorbed, impeding the formation of a capillary layer but distorting the shape of the fungal spore. Typically, fungal spores are much smaller (microns) than pollen grains (tens of microns). When the size of condensation droplets become larger than fungal spores, small fungal spores may be fully embedded inside a micron-sized condensation droplets.
For clarity of exposition,
In an embodiment, one or more condensation countermeasures are implemented in an airborne particle detector having the ability to distinguish between different species of spores or pollen by collecting and interpreting optical data. The nature of optical data varies depending on the nature of the optical system hardware.
A specific embodiment of an airborne particle detector is a detector referred to as SporeCam® by Scanit Technologies of Fremont, Calif. The device can be deployed in indoor or outdoor growing environments to continuously capture airborne particles onto a media cassette. The device uses optics and light fusion to obtain data on particles captured. Data may be transferred to cloud servers (e.g., Amazon Web Services (AWS) servers) for analysis. The Scanit system enables detection of airborne pathogens before infestation so that growers can take preventive actions, optimize pest management practices, minimize yield losses, and have efficacy proof that their actions are working to control disease.
The optical system of Scanit devices may be described as a lens-based microscope. A lens system images particles in a particle inspection zone onto a camera sensor. For example,
There are various implementations of systems and techniques to distinguish between different species of spores or pollens by collecting and interpreting optical data such as discussed in U.S. patent application Ser. No. 16/492,098 (Ozcan) and U.S. Pat. No. 6,594,001 (Yabusaki). While a specific embodiment of condensation countermeasures is directed to a detector having a lens-based microscope, it should be appreciated that the condensation countermeasures described can be applied to other detectors having other optical hardware including those of Ozcan and Yabusaki. That is, water condensation may compromise optical data from the optical systems of Ozcan, Yabusaki, and others; and the condensation countermeasures described may be applied to the Ozcan, Yabusaki, and other systems. A particle detector may be implemented using any one concept or combination of the concepts discussed in this document for condensation countermeasures. A condensation countermeasure as presented in this patent application may be modified as needed for the particular detector application.
For example,
In other words, particles are collected on the surface of the transparent substrate. Captured particles are illuminated by the illumination source generating optical data at the image sensor. Unlike for Scanit optical systems, this optical system contains no lens. As schematically represented by the wavy line drawn above the image sensor, the resulting image is a complex interference pattern, not a direct image of the particles of interest. Nevertheless, with suitable mathematical processing, to a good approximation, such lens-less optical images can be transformed into images similar to images of a more conventional microscope.
The above principles explained in terms of Scanit's optical system also may be applied to the optical system of Ozcan.
As another contrasting example, consider the particle detection optics described in Yabusaki and assigned to Kowa.
In other words, unlike the Scanit and Ozcan devices, particles of interest are optically probed while still suspended in air within a flow cell. Ambient air is sampled and particles of interest are directed into a flow cell. Light from a light source illuminates particles of interest in the flow cell. Scattered or fluorescent light from particles of interest is detected by photomultiplier tubes. Unlike the Scanit and Ozcan systems described above, no 2-D images of particles are generated. Nevertheless, this Yabusaki optical system provides a degree of particle discrimination based on optical data that probes the optical scattering and fluorescence properties of particles.
As conceptually illustrated in
Heating the interior of the device may reduce or eliminate condensation. Less heating energy may be required if a local heater aims only to elevate the temperature locally where particles are inspected.
Referring back now to
In the Ozcan optical system, the signature of the rotationally symmetric smooth rounded shape of water droplets is a rotationally symmetric interference pattern. After mathematical processing to eliminate the interference patterns, the resulting droplet image is expected to remain at least approximately rotationally symmetric. This allows water droplets to flagged for rejection either before or after the mathematical processing.
For airborne particle detectors of the style of Yabusaki, water droplets are even more symmetric. Small water droplets suspended in air are spherical. This high degree of symmetry (rotational symmetry about any axis through the droplet's center) can be expected to result in a distinct optical signature. For example, the optical data after the droplet falls past the optical measurement plane may be a time-reversed copy of the optical data obtained as the droplet approached the optical measurement plane. The optical data for a tumbling non-spherical spore or pollen grain may be expected to produce optical data with more random variations. Here “small” of “small water droplets” means comparable to the size of pollen or spores. Raindrops are too “big” to enter the Yabusaki device. Raindrops are larger than 0.5 mm in diameter and as they fall take the shape of flattened spheroids.
The particle detector executes executable code (or computer-readable code) that embodies a technique or algorithm as described herein. For example, in an embodiment, the particle detector includes a processor, read only memory (ROM) connected to the processor and storing programs, data, images, or combinations of these. Random access memory (RAM) may be connected to the processor such as via a bus. The RAM provides a working storage space for the storage of particle images and data captured by the camera sensor. The processor may be further connected to the light sources, heater, cartridge motor, blower, and other hardware components of the particle detector. The processor may be programmed or configured using the programs and data stored in ROM to activate, deactivate, coordinate, communicate, and interact with these and other hardware components of the particle detector. The processor performs algorithms and directs the overall operation of the particle detector.
Such algorithms may, for example, govern operation of the blower to draw ambient air into the particle detector and towards the tape media of the collection cartridge; operation of the cartridge motor to advance the tape media containing collected particles from the collection zone, past the heater, and to the inspection zone; operation of the light sources to illuminate the particles; operation of the camera sensor to capture the illuminated particles; execution of image recognition logic to detect water droplets; operation of the cartridge motor to rewind the tape media from the inspection zone to the heater; operation of the heater to evaporate the water droplets; other operations as described and combinations of these.
In an embodiment, there is a particle detector (700,
The heater may be positioned upstream of the particle inspection zone with respect to an air flow path (1245,
The opening of the particle detector may include an exterior side (2510A,
In an embodiment, the particle detector includes an optical platform (1210,
In an embodiment, the light source is a first light source of a plurality of light sources (1015A,B,
In an embodiment, the processor is communicatively coupled to a storage device (4917,
In an embodiment, the particle detector includes an optical platform (1210,
In an embodiment, there is a method of operating a particle detector (700,
In an embodiment, the particle detector includes an optical platform (1210,
In an embodiment, the heater includes an axial resistor (1305,
In an embodiment, there is a particle detector (700,
In an embodiment, a particle detector includes: an opening into which ambient air outside the particle detector and comprising particles of interest to collect is drawn; a light source; a heater; a sensor; and a processor, coupled to the light source, heater, and sensor, wherein the heater increases a temperature at a particle inspection zone at which the particles are brought relative to a temperature of the ambient air, the light source illuminates the particles with light, the sensor detects and generates optical data resulting from the particles being illuminated with the light, and the processor analyzes the optical data received from the sensor to identify the particles.
The heater may be positioned upstream of the particle inspection zone. The heater may include: an axial resistor, coupled to the processor; an insulating sleeve, containing the axial resistor, and having ends that are sealed; and an opening formed in the sleeve and exposing a portion of the axial resistor. The opening may include: an exterior side; an interior side, opposite the exterior side; and a concave surface on the interior side and surrounding at least a portion of the opening. The particle detector may include a desiccator.
In an embodiment, the particle detector includes an optical platform, the optical platform comprising: a cartridge well for holding a removable cartridge, the removable cartridge having a first side, and a second side, adjacent to the first side, wherein when the removable cartridge is inserted into the particle detector, the first side faces the opening and the second side is at the particle inspection zone; and a groove into which the heater is recessed.
In an embodiment, a particle detector includes: an opening into which ambient air outside the particle detector and comprising particles of interest to collect is drawn; a light source; a desiccator; a sensor; and a processor, coupled to the light source and sensor, wherein the light source illuminates the particles with light, the sensor detects and generates optical data resulting from the particles being illuminated with the light, the processor analyzes the optical data received from the sensor to identify the particles, and the desiccator reduces humidity inside the particle detector relative to humidity in the ambient air outside the particle detector device.
In an embodiment, a method includes: positioning a plurality of light sources about a particle inspection zone of a particle detector; activating at least some of the plurality of light sources to illuminate particles brought to the particle inspection zone; capturing an image of the particle inspection zone; identifying objects in the image as being specular reflections based on locations of the objects in the image as corresponding to positions of the activated light sources; determining that the objects are water droplets; and rejecting the water droplets from an analysis of the image to identify the particles.
In an embodiment, a method includes: maintaining a library comprising a plurality of reference characteristics for a plurality of spores, the reference characteristics describing the spores under different levels of moisture saturation; acquiring an image of particles collected from ambient air; and selecting a reference characteristic to identify the particles from the image based on moisture levels in the ambient air.
In an embodiment, a method includes: collecting particles from ambient air; detecting condensation in the ambient air; activating countermeasures to compensate for the condensation; detecting a lack of condensation in the ambient air; and deactivating the countermeasures. Activating countermeasures may include increasing an airflow rate of the ambient air into a particle detector. Deactivating the countermeasures may include decreasing an airflow rate of the ambient air into a particle detector.
In an embodiment, a method includes: collecting particles from ambient air onto a tape media of a collection cartridge; advancing a portion of the tape media having the collected particles to a particle inspection zone; and before the portion of the tape media reaches the particle inspection zone, applying heat to the portion of the tape media.
Communication network 4824 may itself be comprised of many interconnected computer systems and communication links. Communication links 4828 may be hardwire links, optical links, satellite or other wireless communications links, wave propagation links, or any other mechanisms for communication of information. Various communication protocols may be used to facilitate communication between the various systems shown in
Distributed computer network 4800 in
Client systems 4813, 4816, and 4819 enable users to access and query information stored by server system 4822. In a specific embodiment, a “Web browser” application executing on a client system enables users to select, access, retrieve, or query information stored by server system 4822. Examples of web browsers include the Internet Explorer® and Edge® browser programs provided by Microsoft® Corporation, Chrome® browser provided by Google®, and the Firefox® browser provided by Mozilla® Foundation, and others. In another specific embodiment, an iOS App or an Android® App on a client tablet enables users to select, access, retrieve, or query information stored by server system 4822. Access to the system can be through a mobile application program or app that is separate from a browser.
A computer-implemented or computer-executable version of the system may be embodied using, stored on, or associated with computer-readable medium or non-transitory computer-readable medium. A computer-readable medium may include any medium that participates in providing instructions to one or more processors for execution. Such a medium may take many forms including, but not limited to, nonvolatile, volatile, and transmission media. Nonvolatile media includes, for example, flash memory, or optical or magnetic disks. Volatile media includes static or dynamic memory, such as cache memory or RAM. Transmission media includes coaxial cables, copper wire, fiber optic lines, and wires arranged in a bus. Transmission media can also take the form of electromagnetic, radio frequency, acoustic, or light waves, such as those generated during radio wave and infrared data communications.
For example, a binary, machine-executable version, of the software of the present system may be stored or reside in RAM or cache memory, or on a mass storage device. The source, executable code, or both of the software may also be stored or reside on a mass storage device (e.g., hard disk, magnetic disk, tape, or CD-ROM). As a further example, code may be transmitted via wires, radio waves, or through a network such as the Internet.
A client computer can be a smartphone, smartwatch, tablet computer, laptop, wearable device or computer (e.g., Google Glass), body-borne computer, or desktop.
Arrows such as 4922 represent the system bus architecture of computer system 4901. However, these arrows are illustrative of any interconnection scheme serving to link the subsystems. For example, speaker 4920 could be connected to the other subsystems through a port or have an internal direct connection to central processor 4902. The processor may include multiple processors or a multicore processor, which may permit parallel processing of information. Computer system 4901 shown in
Computer software products may be written in any of various suitable programming languages, such as Python, C, C++, C#, Pascal, Fortran, Perl, Matlab® (from MathWorks), SAS, SPSS, JavaScript®, AJAX, Java®, SQL, and XQuery (a query language that is designed to process data from XML files or any data source that can be viewed as XML, HTML, or both). The computer software product may be an independent application with data input and data display modules. Alternatively, the computer software products may be classes that may be instantiated as distributed objects. The computer software products may also be component software such as Java Beans® (from Oracle Corporation) or Enterprise Java Beans® (EJB from Oracle Corporation). In a specific embodiment, a computer program product is provided that stores instructions such as computer code to program a computer to perform any of the processes or techniques described.
An operating system for the system may be Raspberry Pi OS by the Rasberry Pi Foundation, iOS by Apple®, Inc., Android by Google®, one of the Microsoft Windows® family of operating systems (e.g., Windows NT®, Windows 2000®, Windows XP®, Windows XP® x64 Edition, Windows 8, Windows 10), Linux, HP-UX, UNIX, Sun OS®, Solaris®, Mac OS X®, Alpha OS®, AIX, IRIX32, or IRIX64. Other operating systems may be used. Microsoft Windows® is a trademark of Microsoft® Corporation.
Furthermore, the computer may be connected to a network and may interface to other computers using this network. The network may be an intranet, internet, or the Internet, among others. The network may be a wired network (e.g., using copper), telephone network, packet network, an optical network (e.g., using optical fiber), or a wireless network, or any combination of these. For example, data and other information may be passed between the computer and components (or steps) of the system using a wireless network using a protocol such as Wi-Fi (IEEE standards 802.11, 802.11a, 802.11b, 802.11e, 802.11g, 802.11i, and 802.11n, just to name a few examples). For example, signals from a computer may be transferred, at least in part, wirelessly to components or other computers.
In an embodiment, with a Web browser executing on a computer workstation system, a user accesses a system on the World Wide Web (WWW) through a network such as the Internet. The Web browser is used to download web pages or other content in various formats including HTML, XML, text, PDF, and postscript, and may be used to upload information to other parts of the system. The Web browser may use uniform resource identifiers (URLs) to identify resources on the Web and hypertext transfer protocol (HTTP) in transferring files on the Web.
In the description above and throughout, numerous specific details are set forth in order to provide a thorough understanding of an embodiment of this disclosure. It will be evident, however, to one of ordinary skill in the art, that an embodiment may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form to facilitate explanation. The description of the preferred embodiments is not intended to limit the scope of the claims appended hereto. Further, in the methods disclosed herein, various steps are disclosed illustrating some of the functions of an embodiment. These steps are merely examples, and are not meant to be limiting in any way. Other steps and functions may be contemplated without departing from this disclosure or the scope of an embodiment. Other embodiments include systems and non-volatile media products that execute, embody or store processes that implement the methods described above.
This application claims priority to U.S. provisional patent application 63/222,585, filed Jul. 16, 2021, and is incorporated by reference along with other cited references in this application.
Number | Date | Country | |
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63222585 | Jul 2021 | US |