WO2014039496A2 - Sensor degradation assessment and correction system - Google Patents

Sensor degradation assessment and correction system Download PDF

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Publication number
WO2014039496A2
WO2014039496A2 PCT/US2013/057951 US2013057951W WO2014039496A2 WO 2014039496 A2 WO2014039496 A2 WO 2014039496A2 US 2013057951 W US2013057951 W US 2013057951W WO 2014039496 A2 WO2014039496 A2 WO 2014039496A2
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WIPO (PCT)
Prior art keywords
sensor
signal
detector
emitter
light
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PCT/US2013/057951
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French (fr)
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WO2014039496A3 (en
Inventor
Samuel R. LANEY
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Woods Hole Oceanographic Institution
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Publication of WO2014039496A2 publication Critical patent/WO2014039496A2/en
Publication of WO2014039496A3 publication Critical patent/WO2014039496A3/en

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/01—Arrangements or apparatus for facilitating the optical investigation
    • G01N21/15—Preventing contamination of the components of the optical system or obstruction of the light path
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/01—Arrangements or apparatus for facilitating the optical investigation
    • G01N21/15—Preventing contamination of the components of the optical system or obstruction of the light path
    • G01N2021/155—Monitoring cleanness of window, lens, or other parts
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/01—Arrangements or apparatus for facilitating the optical investigation
    • G01N21/15—Preventing contamination of the components of the optical system or obstruction of the light path
    • G01N2021/155—Monitoring cleanness of window, lens, or other parts
    • G01N2021/157—Monitoring by optical means

Definitions

  • the invention relates to sensor systems and, more particularly, to systems for adjusting a sensor to compensate for degradation of the sensor caused by exposure to a surrounding environment.
  • Phytoplankton are photosynthetic aquatic microbes that generate roughly half of the planet's primary production. They are critical to the ecology and biogeochemistry of marine ecosystems in all of the world's oceans, even in polar, ice-covered seas where underwater light levels are strongly seasonal and nutrient inputs are low. Long-term assessment of the ecology and biogeochemistry of phytoplankton assemblages in the ocean has traditionally been challenging, given logistical problems with sampling and the high cost of using ships as platforms for oceanographic observations. Robotic, autonomous ocean-observing systems are becoming more widely used for assessing the oceanic distributions and biogeochemistry of phytoplankton, especially in extreme ocean environments such as the ice-covered polar seas.
  • Ice-Tethered Profilers are autonomous systems for deploying sensors over multi-annual time scales under polar ice. Like many other autonomous ocean observing systems, ITPs typically include optical sensors to assess the abundance and other properties of ocean phytoplankton. [0006] Optical sensors utilized with ITPs or other long-term aquatic monitoring systems commonly suffer from biofouling. In general, biofouling is an accumulation of
  • Biofouling reduces the accuracy of optical measurements, for example, by blocking or partially blocking light emitters and/or light receivers associated with optical sensors.
  • embodiments of the present invention feature devices and methods for assessing the performance degradation of a sensing system exposed to a marine or other harsh environment.
  • the devices and methods utilize an emitter (e.g., a light source) and a detector (e.g., a light detector) to assess an amount of degradation associated with the sensing system and to make any required adjustments or corrections to subsequent measurements.
  • an emitter e.g., a light source
  • a detector e.g., a light detector
  • the devices and methods may be applied to degradation of any type (e.g., biofouling, corrosion, dirt accumulation, etc.) and on any component of the sensing system, including an emitter, a detector, or both.
  • any type e.g., biofouling, corrosion, dirt accumulation, etc.
  • any component of the sensing system including an emitter, a detector, or both.
  • the devices and methods are used for monitoring and assessing biofouling on optical sensors used in long-term aquatic deployments.
  • the devices and methods may utilize optical feedback to redirect light from a light source (e.g., in a fluorometer, a backscatter meter, or other sensor with a light) to a light detector (e.g., an irradiance sensor or radiometer).
  • a light source e.g., in a fluorometer, a backscatter meter, or other sensor with a light
  • a light detector e.g., an irradiance sensor or radiometer.
  • the devices and methods are able to detect biofouling and provide data to compensate for the effects of the biofouling.
  • the devices and methods may adjust and/or validate optical data collected by a sensor.
  • the devices and methods described herein provide a unique solution to the problem of degradation of sensing systems, such as biofouling on aquatic optical sensors. Rather than simply reducing the rate of degradation, or removing the degradation itself, the devices and methods detect and assess the influence of the degradation on measurement accuracy.
  • the devices and methods provide a direct, simple, and inexpensive way to obtain accurate and robust measurements in harsh environments, over extended periods of time.
  • the invention in general, in one aspect, relates to a sensor assessment system.
  • the system includes an emitter, a detector, a transmission element for directing a signal from the emitter to the detector, and a processor for adjusting output of a sensor based on the signal to compensate for degradation of the sensor caused by exposure to a surrounding environment. At least one of the emitter and the detector is exposed to the surrounding environment.
  • the emitter includes a light source
  • the detector includes a light detector
  • the transmission element includes an optical transmission element for directing light from the light source to the light detector, and the degradation is or includes biofouling.
  • the sensor includes the light detector.
  • the light source may include a module with an integral light source.
  • the light source module may be, may include, or form part of, for example, a fluorometer, a scattering meter, a transmissometer, and/or a non-sensing light generator.
  • the light detector may be, may include, or form part of, for example, a radiometer, a fluorometer, a transmissometer, a scattering meter, and/or a dedicated light detector.
  • the optical transmission element includes a first end disposed proximate the light source and a second end disposed proximate the light detector.
  • the optical transmission element may be or may include, for example, an optical fiber, a mirror, a gas, a liquid, and/or an optically diffusing material.
  • the system includes an element moveable between a first position covering the sensor and a second position uncovering the sensor.
  • the optical transmission element is disposed on the moveable element.
  • the moveable element may be or may include, for example, a shutter, a brush, and/or a biofouling minimization treated component.
  • the moveable element may include copper, another biofouling resistant material, and/or a material treated with a bioresistant coating.
  • the system includes an actuator to move the optical transmission element and/or the moveable element between the first position and the second position.
  • the system may include a control adapted to trend or adjust sensor output over time, corresponding at least in part to a degree of biofouling of the sensor.
  • the control is further adapted to apply a correction factor to sensor output, based on the degree of biofouling.
  • the invention in another aspect, relates to a method of assessing degradation of a sensor.
  • the method includes: sending an initial signal from an emitter toward a sensor subject to degradation when the sensor is in a clean condition, the sensor having an integral detector; detecting the initial signal with the integral detector and optionally storing an output of the clean condition sensor; thereafter periodically sending a calibration signal from the emitter toward the sensor; and adjusting an output of the sensor based on the calibration signal to compensate for degradation of the sensor caused by exposure to a surrounding environment.
  • the emitter includes a light source
  • the degradation includes biofouling
  • the integral detector includes an optical light detector.
  • the method may include applying a correction factor to sensor output, based on the degree of biofouling.
  • the light source may include a module (e.g., a fluorometer, a scattering meter, a transmissometer, and/or a non-sensing light generator) with an integral light source.
  • the sensor may be or may include, for example, a radiometer, a fluorometer, a transmissometer, a scattering meter, and/or a dedicated light detector.
  • At least one directing step uses an optical transmission element disposed between the light source and the optical detector of the sensor.
  • the optical transmission element may include a first end disposed proximate the light source and a second end disposed proximate the optical detector of the sensor.
  • the method includes the step of moving an element between a first position covering the sensor and a second position uncovering the sensor.
  • the optical transmission element is disposed on the moveable element.
  • the moveable element may be or may include, for example, a shutter, a brush, and/or a biofouling minimization treated component.
  • the optical transmission element is or includes an optical fiber, a mirror, a gas, a liquid, and/or an optically diffusing material.
  • the moveable element may include copper, another biofouling resistant material, a material treated with a bioresistant coating, and combinations thereof.
  • the method includes the step of energizing an actuator to move the optical transmission element and/or the moveable element between the first position and the second position.
  • the invention relates to a sensor assessment system.
  • the system includes a sensor having a detector exposed to a surrounding environment, a reference emitter protected from the surrounding environment, a transmission element for directing a signal from the reference emitter to the detector, and a processor for adjusting output of the sensor based on the signal to compensate for degradation of the sensor caused by exposure to the surrounding environment.
  • the degradation is or includes biofouling, dirt
  • the signal may be, for example, an acoustic signal, a thermal signal, a radio wave signal, a microwave signal, an infrared signal, a visible light signal, an ultraviolet light signal, an x-ray signal, and an electrical signal.
  • the senor further includes an emitter exposed to the surrounding environment
  • the system further includes (i) a reference detector protected from the surrounding environment, and (ii) a second transmission element for directing a second signal from the emitter to the reference detector
  • the processor is for adjusting output of the sensor based on the second signal to compensate for degradation of the sensor caused by exposure to the surrounding environment.
  • the invention in another aspect, relates to a method of assessing degradation of a sensor.
  • the method includes: sending a first signal from an emitter to a detector, the emitter and the detector forming at least part of a sensor exposed to a surrounding environment;
  • the degradation is or includes biofouling, dirt
  • the first signal and the second signal may each independently include or be, for example, an acoustic signal, a thermal signal, a radio wave signal, a microwave signal, an infrared signal, a visible light signal, an ultraviolet light signal, an x-ray signal, and/or an electrical signal.
  • FIG. 1 is a schematic diagram of a sensor assessment system, in accordance with one embodiment of the invention.
  • FIG. 2 is a schematic diagram of a sensor assessment system having a transmission element, in accordance with one embodiment of the invention.
  • FIG. 3 is a schematic diagram of a sensor assessment system having a reflective transmission element, in accordance with one embodiment of the invention.
  • FIG. 4 is a schematic diagram of a sensor assessment system having a reference emitter and a reference detector, in accordance with one embodiment of the invention
  • FIG. 5 is a schematic diagram of a sensor assessment system having a reference emitter, in accordance with one embodiment of the invention.
  • FIG. 6 is a schematic diagram of a sensor assessment system having a reference detector, in accordance with one embodiment of the invention.
  • FIG. 7 is a schematic, perspective view of an aquatic optical device, in accordance with one embodiment of the invention.
  • FIG. 8 is a photograph of an aquatic optical device having a transmission element, in accordance with one embodiment of the invention.
  • apparatus, systems, methods, and processes of the claimed invention encompass variations and adaptations developed using information from the embodiments described herein. Adaptation and/or modification of the apparatus, systems, methods, and processes described herein may be performed by those of ordinary skill in the relevant art.
  • an emitter and/or a detector are used to detect and/or compensate for degradation of a sensor exposed to a harsh environment.
  • the emitter may be any type of emitter that transmits a signal.
  • the emitter may transmit an acoustic signal, a thermal signal (e.g., heat), an electromagnetic signal (e.g., radio waves, microwaves, infrared radiation, visible light, ultraviolet light, and/or x-rays), and/or an electrical signal.
  • the detector may be any type of detector capable of receiving any type of signal from an emitter, including an acoustic signal, a thermal signal, an electromagnetic signal, and/or an electrical signal.
  • the degradation experienced by the sensor may be any type of degradation, including biofouling, dirt accumulation, oil accumulation, salt and precipitate coating, extraction of plasticizers (e.g., from a transparent sensor surface), sensor surface scratching or cracking, corrosion, rust (particularly important in acoustic embodiments), and/or permeation of liquids, gases, or salts. While much of the discussion herein focuses on degradation caused by biofouling, embodiments of the invention are not limited to biofouling as the only type of degradation. Any type of degradation may be assessed and/or compensated for using the systems, devices, and methods described herein.
  • the harsh environment in which the emitter and the detector are used may be any type of harsh environment, including an aquatic environment (e.g., an oceanographic environment), a dusty environment, a corrosive environment, a high or low pH environment, a high or low temperature environment, a high radiation environment, a biological environment, an industrial environment, a manufacturing environment, and/or a machine environment (e.g., an engine or an electromechanical device). While much of the discussion herein focuses on an aquatic environment, embodiments of the invention are not limited to use in or with aquatic environments. The systems, devices, and methods described herein may be used in any type of environment where sensor degradation may occur.
  • an aquatic environment e.g., an oceanographic environment
  • a dusty environment e.g., a dusty environment, a corrosive environment, a high or low pH environment, a high or low temperature environment, a high radiation environment, a biological environment, an industrial environment, a manufacturing environment, and/or a machine environment (e.g., an engine
  • a sensing device e.g., an aquatic optical device
  • a sensor assessment system 10 having an emitter 12, a transmission element 14, and a detector 16.
  • the emitter 12 emits a signal (e.g., light)
  • the transmission element 14 directs the signal to the detector 16, and the detector 16 measures or detects the signal.
  • degradation e.g., biofouling
  • the intensity and/or frequency spectrum of the signal received by the detector 16 may change. By measuring these changes, the degradation may be assessed, and measurements obtained by the sensing device may be adjusted and/or validated, as required.
  • the emitter 12 is or includes any type of light generating component, such as an LED, an incandescent bulb, and/or a laser.
  • the emitter 12 may be a standalone light source, and/or the emitter 12 may be integrated into one or more optical sensors on the sensing device.
  • the emitter 12 may be part of a fluorometer or other optical sensor. Maximum, minimum, and typical values for wavelengths emitted by the emitter 12 are provided in Table 1.
  • the detector 16 may be any type of light measuring or detecting device, such as a photoresistor, a photovoltaic cell, a photodiode, a phototube, imaging devices, other forms of photosensors, and combinations thereof.
  • the detector 16 may be a standalone light detector, and/or the detector 16 may be integrated into one or more optical sensors on the sensing device.
  • the detector 16 may be integrated into a fluorometer or a photosynthetically active radiation (PAR) sensor.
  • PAR photosynthetically active radiation
  • the transmission element 14 may be any type of device that directs or transmits the signal from the emitter to the detector.
  • the transmission element 14 may be or may include a waveguide, a reflective surface (e.g., a mirror), a gas, a liquid, an optically diffusing material, and combinations thereof.
  • the waveguide may be configured to transmit or guide electromagnetic signals (e.g., visible light, microwaves, infrared radiation, UV light, and/or radio waves), acoustic energy, electrical energy, and/or thermal energy.
  • the transmission element 14 may include an optical fiber.
  • the transmission element 14 may include one or more apertures (e.g., lenses) to collect light or other signals from the emitter 12 and/or emit the signals to the detector 16.
  • the transmission element 14 is movable between an active position in which the transmission element 14 directs a signal from the emitter 12 to the detector 16, and an inactive position in which the transmission element 14 does not direct a signal from the emitter 12 to the detector 16.
  • the inactive position for example, the detector 16 may measure light from the surroundings, rather than from the emitter 12.
  • the transmission element 14 may include a waveguide or optical fiber 18 that directs light or another type of signal (e.g., acoustic energy) along a curved or bent path.
  • the optical fiber 18 may include one or more fibers made of glass (e.g., silica, fluorozirconate, fluoroaluminate, and chalcogenide), crystalline materials (e.g., sapphire), and/or plastic.
  • the optical fiber 18 is a rigid fused glass fiber.
  • the optical fiber 18 may be flexible.
  • the transmission element 14 includes a reflective surface 20 that reflects the signal from the emitter 12 to the detector 16.
  • the reflective surface 20 may be any type of reflective surface, such as a mirror, a diffuser, and/or a light colored surface (e.g., a diffuse plastic, such as white acetal).
  • the reflective surface 20 is preferably used when the emitter 12 and detector 16 are in close proximity with one another.
  • the reflective surface 20 may be positioned in front of a sensor that includes both the emitter 12 and the detector 16 (e.g., a fluorometer).
  • a system 40 for assessing sensor degradation includes a sensor 42 exposed to a surrounding environment, a reference emitter 44 protected from the environment, and a reference detector 46 also protected from the environment.
  • the sensor 42 includes a sensor emitter 48 that may be similar to or a duplicate of the reference emitter 44.
  • the sensor 42 also includes a sensor detector 50 that may be similar to or a duplicate of the reference detector 46.
  • Each of the detectors in the system is configured to receive a signal from each of the emitters.
  • the sensor detector 50 is configured to receive a signal 51 from the sensor emitter 48 via transmission element 52 or a signal 53 from the reference emitter 44 via transmission element 54.
  • the reference detector 46 is configured to receive a signal 55 from the sensor emitter 48 via transmission element 56 or a signal 57 from the reference emitter 44 via transmission element 58.
  • the protected reference emitter 44 and reference detector 46 allows the sensor 42 to be assessed for degradation.
  • the reference detector 46 may periodically receive the signal 55 (e.g., a calibration signal) from the sensor emitter 48 via transmission element 56.
  • the signal 55 may then be compared to the signal 51 received by the sensor detector 50 from the sensor emitter 48 via transmission element 52. Differences between the two signals may be used to assess the degradation of the sensor detector 50 due to exposure in the surrounding environment.
  • the sensor detector 50 may be recalibrated or adjusted accordingly to compensate for the degradation.
  • the reference emitter 44 may periodically transmit the signal 53 (e.g., a calibration signal) to the sensor detector 50 via transmission element 54.
  • the signal 53 may then be compared to the signal 51 received by the sensor detector 50 from the sensor emitter 48 via transmission element 52. Differences between the two signals may be used to assess the degradation of the sensor emitter 48 due to exposure in the surrounding environment. Any necessary adjustments to sensor measurements may be made accordingly.
  • the reference emitter 44 and/or the reference detector 46 may be assessed for degradation by periodically sending the signal 57 from the reference emitter 44 to the reference detector 46 via transmission element 58.
  • the signal 57 may be compared with one or more previous signals transmitted from the reference emitter 44 to the reference detector 46 to identify any differences (e.g., in signal intensity or frequency content) between the signal 57 and the previous signal(s). Such differences may be indicative of degradation, and the system 40 may adjust measurements or sensor output accordingly.
  • the reference emitter 44 and the reference detector 46 may be covered by or enclosed within at least one protective member 60.
  • the protective member 60 may include, for example, a sealed container, a surface treatment or coating, a solid barrier, a movable shutter or barrier, an anti-fouling material, and a toxic material.
  • the reference emitter 44 and/or the reference detector 46 may be periodically cleaned or scrubbed (e.g., with a brush, mechanical action, and/or UV light) to remove or reduce any degradation.
  • the system 40 is depicted as including both the reference emitter 44 and the reference detector 46, in alternative embodiments one or both of these reference elements may not be included.
  • a system 62 for assessing sensor degradation does not include a sensor emitter and therefore may not need a reference detector (e.g., to assess the degradation of the sensor emitter).
  • the system 62 in this case may include the reference emitter 44 for sending the signal 53 to the sensor detector 50 via transmission element 54.
  • a system 64 for assessing sensor degradation does not include a sensor detector and therefore may not need a reference emitter (e.g., to assess the degradation of the sensor detector).
  • the system 64 in this case may include the reference detector 46 for receiving the signal 55 from the sensor emitter 48 via transmission element 56.
  • the systems and methods described herein are used to assess and/or compensate for degradation associated with a sensor.
  • a signal from an emitter to a detector may be used to detect sensor degradation, and output from the sensor (e.g., a voltage or sampled numerical values) may be adjusted or calibrated to compensate for the degradation.
  • the emitter and/or the detector form at least part of the sensor.
  • the detector may be disposed within the sensor and the emitter may be outside the sensor but configured to send a signal (e.g., acoustic energy or light) to the detector.
  • the emitter and the detector may not form part of the sensor.
  • the sensor may not include the detector and may not receive a signal from the emitter.
  • a signal from the emitter to the detector may be used to determine an amount of degradation associated with or in the vicinity of the emitter and the detector and, based on that amount, adjust an output from the sensor accordingly.
  • a relationship between sensor performance and the degradation associated with the emitter and the detector may have been previously determined (e.g., in the form of look-up tables or calibration curves).
  • FIG. 7 depicts an aquatic optical device 70 for performing optical measurements in an aquatic environment, in accordance with certain embodiments of the invention.
  • the optical device 70 includes a fluorometer 72 (e.g., a custom WET LABS FLBBCD fluorescence sensor) and a photosynthetically active radiation (PAR) sensor 74 (e.g., a SATLANTIC PAR-LOG- 2000m irradiance sensor).
  • the optical device 70 also includes a sensor 76 for measuring salinity, temperature, pressure, and/or dissolved oxygen (e.g., a SEABIRD SBE41CP CTD sensor with an integrated DO sensor).
  • the optical device 70 may be used to perform various optical measurements, including fluorescence due to CDOM, chlorophyll, phycoerythrin, phycocyanin, rhodamine fluorescence, and uranine.
  • the optical device 70 includes a shutter 78 and an actuator 80.
  • the actuator 80 may be used to cycle the shutter 78 between an open position (in which the sensors are uncovered) and a closed position (in which the sensors are covered).
  • the shutter 78 is configured to cover and protect the sensors when aquatic measurements are not being performed.
  • the specific embodiment depicted in FIG. 7 is an ITP autonomous observing system.
  • the shutter 78 may include or consist of a fouling-resistant material or have a fouling resistant surface.
  • the shutter 78 may be made of a naturally toxic material, such as copper or silver, and/or may include a fouling-resistant coating.
  • the shutter 78 is made of plastic and is coated with a biofouling paint.
  • the actuator 80 may be, for example, a SATLANTIC BIO SHUTTER actuator.
  • the transmission element 14 of the aquatic optical device 70 is attached to the shutter 78. Actuation of the shutter 78 may cycle the transmission element 14 between the active and inactive positions. For example, when the shutter 78 is closed, the transmission element 14 may be in the active position, for directing light from the light source (e.g., the fluorometer 72) to the light detector (e.g., the PAR sensor 74).
  • the transmission element 14 is a U-shaped, potted optical fiber. Alternatively or additionally, the transmission element 14 may be or may include a reflective surface.
  • a bottom surface of the shutter 78 may include a mirror or white acetal to reflect light from the light source to the light detector.
  • the aquatic optical device 70 allows the degree of biofouling accumulation to be monitored and assessed over time. As biofouling accumulates on the aquatic optical device 70, data collected by the sensors may be adjusted and/or validated, as needed, based on the biofouling assessment. In one embodiment, an initial calibration of the emitter 12, the transmission element 14, and the detector 16 is performed in clean water with clean surfaces, before the optical device 70 has been deployed in an aquatic environment.
  • biofouling reduces the amount of light transmitted from the emitter 12 to the detector 16.
  • optical data from one or more sensors on the optical device 70 may be corrected accordingly. For example, if the biofouling is found to reduce the amount of light received by the detector 16 by ten percent, light intensity values received by a sensor during aquatic measurements may be corrected by ten percent, to compensate for the biofouling.
  • optical data collected by the sensors may also be adjusted based on changes in the frequency spectrum of the detected light, due to the biofouling. To adjust the optical data, a sensor gain and/or a sensor bias may be adjusted, as desired.
  • the shutter 78 includes a cleaning device (e.g., a brush or a blade) for reducing the accumulation of biofouling on the aquatic optical device 70.
  • the cleaning device may be attached to the bottom surface of the shutter 78.
  • the cleaning device may scrub or wipe a sensor (e.g., an optical face of the sensor), the emitter 12, and/or the detector 16. Cleaning the emitter 12 and/or the detector 16 in addition to the sensor may keep the biofouling consistent among the sensor, the emitter 12, and/or the detector 16.
  • the shutter 78 actuates to a third position (i.e., a cleaning position) to allow the brush (or other cleaning device) to perform the cleaning function.
  • a third position i.e., a cleaning position
  • Use of the cleaning device may prolong the usable life of the aquatic optical device and/or improve measurement accuracy.
  • the biofouling assessment system 10 is used as a biofouling sensor to measure the biofouling process itself, rather than or in addition to assessing biofouling for the purpose of adjusting data collected by an optical sensor.
  • the emitter 12 and the detector 16 may be used to measure the amount of biofouling that occurs over time, as a function of the frequency of cleaning (e.g., once per day or once per month) and/or other cleaning parameters, such as the type of brush and the speed of the brush.
  • the biofouling assessment system 10 may also be used to assess biofouling rates in different regions of the ocean, for example, as a function of environmental parameters, such as salinity, temperature, pressure, biological productivity, and/or dissolved oxygen.
  • the biofouling assessment system 10 may therefore act as a biofouling meter, suitable for long-term autonomous deployments.
  • Some sensors such as a radiometer or a PAR irradiance sensor, generally require the optical face of the sensor to remain unblocked or uncovered for extended periods of time, as measurements are performed.
  • the biofouling assessment system 10 may be mounted to one or more other components of the optical device 70 (i.e., instead of the shutter 78), which may or may not be actuated.
  • the emitter 12, the detector 16, and the transmission element 14 are housed within a common housing.
  • the emitter 12 and/or the detector 16 are configured to be moved into position with respect to one or more sensors on the aquatic optical device 12.
  • the emitter 12 and/or the detector 16 may be attached to the shutter 78, and the shutter 78 may move the emitter 12 and/or the detector 16 in front of a sensor.
  • the transmission element 14 may be the fluid (e.g., water) between the shutter 78 and the sensor.
  • light from a sensor may pass through the fluid to the detector 16, and/or light from the emitter 12 may pass through the fluid to the sensor.
  • the aquatic optical device includes more than one transmission element 14.
  • a first transmission element 14 may include an optical fiber
  • a second transmission element 14 may include a reflective surface, such as a diffuser or mirror.
  • the transmission elements 14 may be attached to the shutter 78 or other actuation device, which may be cycled among multiple positions.
  • the shutter 78 may have a fully open position in which no transmission element 14 is in front of a sensor.
  • the shutter may also have a first position in which the first transmission element 14 is in front of a sensor, and a second position in which the second transmission element 14 is in front of the same or different sensor.
  • the transmission elements 14 may be in their active positions simultaneously, or at different times. Any combination of transmission elements 14, light sources 12, light detectors 16, and/or cleaning devices may be incorporated onto the shutter 78, and the shutter 78 may be actuated to multiple positions to achieve the desired placement of each component.
  • the emitter 12 and/or the detector 16 may be integrated into one or more optical sensors, such as a fluorometer and/or a PAR sensor. Alternatively or additionally, the emitter 12 and/or the detector 16 may not be integrated into one or more optical sensors and may have no other purpose than to assess the amount of biofouling that has occurred on the aquatic optical device 70.
  • a custom light detector i.e., a light detector that is not integrated into a sensor
  • a custom light source i.e., a light source that is not integrated into a sensor.
  • a custom light detector may be used to detect light from a sensor (e.g., a fluorometer), a custom light source may be used to provide light to a sensor (e.g., a PAR sensor), and/or a pair of sensors (e.g., a PAR sensor and a fluorometer) may be coupled with a custom light source and custom light detector.
  • Biofouling may be assessed continually or intermittently (e.g., only when the shutter is closed), using the biofouling assessment system.
  • the devices and methods described herein, including aquatic optical device 70, may be utilized in any aquatic environment.
  • the devices and methods may be used in salt water, fresh water, the ocean, a lake, a river, a pond, an aquifer, a drinking water supply, a pipeline, a swimming pool, or any other body of water.
  • the devices and methods described herein may be used with any type of optical sensor.
  • the optical sensor may be for measuring biological properties, and/or the optical sensor may be for measuring non-biological properties.
  • the optical sensor may be or may include, for example, a fluorometer, a radiometer, a PAR sensor, and/or a dissolved oxygen sensor.
  • each numerical value presented herein for example, in a table, a chart, or a graph, is contemplated to represent a minimum value or a maximum value in a range for a corresponding parameter. Accordingly, when added to the claims, the numerical value provides express support for claiming the range, which may lie above or below the numerical value, in accordance with the teachings herein. Absent inclusion in the claims, each numerical value presented herein is not to be considered limiting in any regard. [0068]
  • the terms and expressions employed herein are used as terms and expressions of description and not of limitation, and there is no intention, in the use of such terms and expressions, of excluding any equivalents of the features shown and described or portions thereof.

Abstract

A sensor degradation assessment system includes an emitter, a detector, and a transmission element for directing a signal from the emitter to the detector. Based on the signal, sensor output is adjusted to compensate for degradation of the sensor caused by exposure to a surrounding environment. The emitter and/or the detector may also be exposed to the surrounding environment.

Description

SENSOR DEGRADATION ASSESSMENT AND CORRECTION SYSTEM
Cross-Reference to Related Application
[0001] This application claims priority to and the benefit of, and incorporates herein by reference in its entirety, U.S. Provisional Patent Application No. 61/696,369, which was filed on September 4, 2012.
Technical Field
[0002] In various embodiments, the invention relates to sensor systems and, more particularly, to systems for adjusting a sensor to compensate for degradation of the sensor caused by exposure to a surrounding environment.
Statement of Government Support
[0003] This invention was made with Government support under Grant No. ARC-0856479 awarded by the National Science Foundation. The Government has certain rights in this invention.
Background
[0004] Phytoplankton are photosynthetic aquatic microbes that generate roughly half of the planet's primary production. They are critical to the ecology and biogeochemistry of marine ecosystems in all of the world's oceans, even in polar, ice-covered seas where underwater light levels are strongly seasonal and nutrient inputs are low. Long-term assessment of the ecology and biogeochemistry of phytoplankton assemblages in the ocean has traditionally been challenging, given logistical problems with sampling and the high cost of using ships as platforms for oceanographic observations. Robotic, autonomous ocean-observing systems are becoming more widely used for assessing the oceanic distributions and biogeochemistry of phytoplankton, especially in extreme ocean environments such as the ice-covered polar seas.
[0005] Ice-Tethered Profilers (ITPs) are autonomous systems for deploying sensors over multi-annual time scales under polar ice. Like many other autonomous ocean observing systems, ITPs typically include optical sensors to assess the abundance and other properties of ocean phytoplankton. [0006] Optical sensors utilized with ITPs or other long-term aquatic monitoring systems commonly suffer from biofouling. In general, biofouling is an accumulation of
microorganisms, plants, or animals that occurs on wetted surfaces. Biofouling reduces the accuracy of optical measurements, for example, by blocking or partially blocking light emitters and/or light receivers associated with optical sensors.
[0007] Current devices and methods for addressing biofouling focus on preventing or removing the biofouling, rather than measuring the biofouling or providing data regarding the magnitude and impact of the biofouling on measurements of interest. Without any quantitative, independent measurement of the biofouling, robust, long-term measurements of optical properties in the ocean are difficult or impossible to validate with any accuracy.
[0008] Needs exist, therefore, for improved devices and methods for monitoring biofouling and other types of degradation on sensor systems and compensating for measurement inaccuracies associated with the degradation of sensor systems in oceanographic or other harsh environments.
Summary of the Invention
[0009] In general, embodiments of the present invention feature devices and methods for assessing the performance degradation of a sensing system exposed to a marine or other harsh environment. The devices and methods utilize an emitter (e.g., a light source) and a detector (e.g., a light detector) to assess an amount of degradation associated with the sensing system and to make any required adjustments or corrections to subsequent measurements.
Advantageously, the devices and methods may be applied to degradation of any type (e.g., biofouling, corrosion, dirt accumulation, etc.) and on any component of the sensing system, including an emitter, a detector, or both.
[0010] In some embodiments, the devices and methods are used for monitoring and assessing biofouling on optical sensors used in long-term aquatic deployments. The devices and methods may utilize optical feedback to redirect light from a light source (e.g., in a fluorometer, a backscatter meter, or other sensor with a light) to a light detector (e.g., an irradiance sensor or radiometer). By monitoring changes in the optical feedback that occur over time, the devices and methods are able to detect biofouling and provide data to compensate for the effects of the biofouling. For example, the devices and methods may adjust and/or validate optical data collected by a sensor. [0011] The devices and methods described herein provide a unique solution to the problem of degradation of sensing systems, such as biofouling on aquatic optical sensors. Rather than simply reducing the rate of degradation, or removing the degradation itself, the devices and methods detect and assess the influence of the degradation on measurement accuracy. The devices and methods provide a direct, simple, and inexpensive way to obtain accurate and robust measurements in harsh environments, over extended periods of time.
[0012] In general, in one aspect, the invention relates to a sensor assessment system. The system includes an emitter, a detector, a transmission element for directing a signal from the emitter to the detector, and a processor for adjusting output of a sensor based on the signal to compensate for degradation of the sensor caused by exposure to a surrounding environment. At least one of the emitter and the detector is exposed to the surrounding environment.
[0013] In certain embodiments, the emitter includes a light source, the detector includes a light detector, the transmission element includes an optical transmission element for directing light from the light source to the light detector, and the degradation is or includes biofouling. In one embodiment, the sensor includes the light detector. The light source may include a module with an integral light source. The light source module may be, may include, or form part of, for example, a fluorometer, a scattering meter, a transmissometer, and/or a non-sensing light generator. The light detector may be, may include, or form part of, for example, a radiometer, a fluorometer, a transmissometer, a scattering meter, and/or a dedicated light detector. In various embodiments, the optical transmission element includes a first end disposed proximate the light source and a second end disposed proximate the light detector. The optical transmission element may be or may include, for example, an optical fiber, a mirror, a gas, a liquid, and/or an optically diffusing material.
[0014] In some embodiments, the system includes an element moveable between a first position covering the sensor and a second position uncovering the sensor. In one embodiment, the optical transmission element is disposed on the moveable element. The moveable element may be or may include, for example, a shutter, a brush, and/or a biofouling minimization treated component. The moveable element may include copper, another biofouling resistant material, and/or a material treated with a bioresistant coating.
[0015] In certain embodiments, the system includes an actuator to move the optical transmission element and/or the moveable element between the first position and the second position. The system may include a control adapted to trend or adjust sensor output over time, corresponding at least in part to a degree of biofouling of the sensor. In one embodiment, the control is further adapted to apply a correction factor to sensor output, based on the degree of biofouling.
[0016] In another aspect, the invention relates to a method of assessing degradation of a sensor. The method includes: sending an initial signal from an emitter toward a sensor subject to degradation when the sensor is in a clean condition, the sensor having an integral detector; detecting the initial signal with the integral detector and optionally storing an output of the clean condition sensor; thereafter periodically sending a calibration signal from the emitter toward the sensor; and adjusting an output of the sensor based on the calibration signal to compensate for degradation of the sensor caused by exposure to a surrounding environment.
[0017] In certain embodiments, the emitter includes a light source, the degradation includes biofouling, and the integral detector includes an optical light detector. The method may include applying a correction factor to sensor output, based on the degree of biofouling. The light source may include a module (e.g., a fluorometer, a scattering meter, a transmissometer, and/or a non-sensing light generator) with an integral light source. The sensor may be or may include, for example, a radiometer, a fluorometer, a transmissometer, a scattering meter, and/or a dedicated light detector.
[0018] In some embodiments, at least one directing step uses an optical transmission element disposed between the light source and the optical detector of the sensor. The optical transmission element may include a first end disposed proximate the light source and a second end disposed proximate the optical detector of the sensor. In one embodiment, the method includes the step of moving an element between a first position covering the sensor and a second position uncovering the sensor. The optical transmission element is disposed on the moveable element. The moveable element may be or may include, for example, a shutter, a brush, and/or a biofouling minimization treated component.
[0019] In certain embodiments, the optical transmission element is or includes an optical fiber, a mirror, a gas, a liquid, and/or an optically diffusing material. The moveable element may include copper, another biofouling resistant material, a material treated with a bioresistant coating, and combinations thereof. In various embodiments, the method includes the step of energizing an actuator to move the optical transmission element and/or the moveable element between the first position and the second position. [0020] In another aspect, the invention relates to a sensor assessment system. The system includes a sensor having a detector exposed to a surrounding environment, a reference emitter protected from the surrounding environment, a transmission element for directing a signal from the reference emitter to the detector, and a processor for adjusting output of the sensor based on the signal to compensate for degradation of the sensor caused by exposure to the surrounding environment.
[0021] In certain embodiments, the degradation is or includes biofouling, dirt
accumulation, salt coating, precipitate coating, extraction of plasticizers, sensor surface scratching, sensor surface cracking, corrosion, rust, liquid permeation, gas permeation, and salt permeation. The signal may be, for example, an acoustic signal, a thermal signal, a radio wave signal, a microwave signal, an infrared signal, a visible light signal, an ultraviolet light signal, an x-ray signal, and an electrical signal. In some embodiments, the sensor further includes an emitter exposed to the surrounding environment, the system further includes (i) a reference detector protected from the surrounding environment, and (ii) a second transmission element for directing a second signal from the emitter to the reference detector, and the processor is for adjusting output of the sensor based on the second signal to compensate for degradation of the sensor caused by exposure to the surrounding environment.
[0022] In another aspect, the invention relates to a method of assessing degradation of a sensor. The method includes: sending a first signal from an emitter to a detector, the emitter and the detector forming at least part of a sensor exposed to a surrounding environment;
sending a second signal from a reference emitter to the detector, the reference emitter being protected from the surrounding environment; comparing the first signal with the second signal; and based on the comparison, adjusting an output from the sensor to compensate for degradation of the sensor caused by exposure to the surrounding environment.
[0023] In certain embodiments, the degradation is or includes biofouling, dirt
accumulation, salt coating, precipitate coating, extraction of plasticizers, sensor surface scratching, sensor surface cracking, corrosion, rust, liquid permeation, gas permeation, and salt permeation. The first signal and the second signal may each independently include or be, for example, an acoustic signal, a thermal signal, a radio wave signal, a microwave signal, an infrared signal, a visible light signal, an ultraviolet light signal, an x-ray signal, and/or an electrical signal. [0024] These and other objects, along with advantages and features of embodiments of the present invention herein disclosed, will become more apparent through reference to the following description, the figures, and the claims. Furthermore, it is to be understood that the features of the various embodiments described herein are not mutually exclusive and can exist in various combinations and permutations.
Brief Description of the Drawings
[0025] In the drawings, like reference characters generally refer to the same parts throughout the different views. Also, the drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention. In the following description, various embodiments of the present invention are described with reference to the following drawings, in which:
[0026] FIG. 1 is a schematic diagram of a sensor assessment system, in accordance with one embodiment of the invention;
[0027] FIG. 2 is a schematic diagram of a sensor assessment system having a transmission element, in accordance with one embodiment of the invention;
[0028] FIG. 3 is a schematic diagram of a sensor assessment system having a reflective transmission element, in accordance with one embodiment of the invention;
[0029] FIG. 4 is a schematic diagram of a sensor assessment system having a reference emitter and a reference detector, in accordance with one embodiment of the invention;
[0030] FIG. 5 is a schematic diagram of a sensor assessment system having a reference emitter, in accordance with one embodiment of the invention;
[0031] FIG. 6 is a schematic diagram of a sensor assessment system having a reference detector, in accordance with one embodiment of the invention;
[0032] FIG. 7 is a schematic, perspective view of an aquatic optical device, in accordance with one embodiment of the invention; and
[0033] FIG. 8 is a photograph of an aquatic optical device having a transmission element, in accordance with one embodiment of the invention.
Description
[0034] It is contemplated that apparatus, systems, methods, and processes of the claimed invention encompass variations and adaptations developed using information from the embodiments described herein. Adaptation and/or modification of the apparatus, systems, methods, and processes described herein may be performed by those of ordinary skill in the relevant art.
[0035] Throughout the description, where apparatus and systems are described as having, including, or comprising specific components, or where processes and methods are described as having, including, or comprising specific steps, it is contemplated that, additionally, there are apparatus and systems of the present invention that consist essentially of, or consist of, the recited components, and that there are processes and methods according to the present invention that consist essentially of, or consist of, the recited processing steps.
[0036] It should be understood that the order of steps or order for performing certain actions is immaterial so long as the invention remains operable. Moreover, two or more steps or actions may be conducted simultaneously.
[0037] In certain embodiments, an emitter and/or a detector are used to detect and/or compensate for degradation of a sensor exposed to a harsh environment. The emitter may be any type of emitter that transmits a signal. For example, the emitter may transmit an acoustic signal, a thermal signal (e.g., heat), an electromagnetic signal (e.g., radio waves, microwaves, infrared radiation, visible light, ultraviolet light, and/or x-rays), and/or an electrical signal. The detector may be any type of detector capable of receiving any type of signal from an emitter, including an acoustic signal, a thermal signal, an electromagnetic signal, and/or an electrical signal.
[0038] Additionally, the degradation experienced by the sensor may be any type of degradation, including biofouling, dirt accumulation, oil accumulation, salt and precipitate coating, extraction of plasticizers (e.g., from a transparent sensor surface), sensor surface scratching or cracking, corrosion, rust (particularly important in acoustic embodiments), and/or permeation of liquids, gases, or salts. While much of the discussion herein focuses on degradation caused by biofouling, embodiments of the invention are not limited to biofouling as the only type of degradation. Any type of degradation may be assessed and/or compensated for using the systems, devices, and methods described herein.
[0039] Further, the harsh environment in which the emitter and the detector are used may be any type of harsh environment, including an aquatic environment (e.g., an oceanographic environment), a dusty environment, a corrosive environment, a high or low pH environment, a high or low temperature environment, a high radiation environment, a biological environment, an industrial environment, a manufacturing environment, and/or a machine environment (e.g., an engine or an electromechanical device). While much of the discussion herein focuses on an aquatic environment, embodiments of the invention are not limited to use in or with aquatic environments. The systems, devices, and methods described herein may be used in any type of environment where sensor degradation may occur.
[0040] Referring to FIG. 1, in various embodiments, a sensing device (e.g., an aquatic optical device) includes a sensor assessment system 10 having an emitter 12, a transmission element 14, and a detector 16. The emitter 12 emits a signal (e.g., light), the transmission element 14 directs the signal to the detector 16, and the detector 16 measures or detects the signal. As degradation (e.g., biofouling) occurs or accumulates in or on the sensing device, the intensity and/or frequency spectrum of the signal received by the detector 16 may change. By measuring these changes, the degradation may be assessed, and measurements obtained by the sensing device may be adjusted and/or validated, as required.
[0041] In some embodiments, the emitter 12 is or includes any type of light generating component, such as an LED, an incandescent bulb, and/or a laser. The emitter 12 may be a standalone light source, and/or the emitter 12 may be integrated into one or more optical sensors on the sensing device. For example, the emitter 12 may be part of a fluorometer or other optical sensor. Maximum, minimum, and typical values for wavelengths emitted by the emitter 12 are provided in Table 1.
[0042] Likewise, the detector 16 may be any type of light measuring or detecting device, such as a photoresistor, a photovoltaic cell, a photodiode, a phototube, imaging devices, other forms of photosensors, and combinations thereof. Like the emitter 12, the detector 16 may be a standalone light detector, and/or the detector 16 may be integrated into one or more optical sensors on the sensing device. For example, the detector 16 may be integrated into a fluorometer or a photosynthetically active radiation (PAR) sensor.
[0043] In general, the transmission element 14 may be any type of device that directs or transmits the signal from the emitter to the detector. For example, the transmission element 14 may be or may include a waveguide, a reflective surface (e.g., a mirror), a gas, a liquid, an optically diffusing material, and combinations thereof. When the transmission element 14 includes a waveguide, the waveguide may be configured to transmit or guide electromagnetic signals (e.g., visible light, microwaves, infrared radiation, UV light, and/or radio waves), acoustic energy, electrical energy, and/or thermal energy. When the transmission element 14 is configured to transmit light, the transmission element 14 may include an optical fiber. The transmission element 14 may include one or more apertures (e.g., lenses) to collect light or other signals from the emitter 12 and/or emit the signals to the detector 16.
[0044] In some implementations, the transmission element 14 is movable between an active position in which the transmission element 14 directs a signal from the emitter 12 to the detector 16, and an inactive position in which the transmission element 14 does not direct a signal from the emitter 12 to the detector 16. In the inactive position, for example, the detector 16 may measure light from the surroundings, rather than from the emitter 12.
Figure imgf000010_0001
Table 1. Exemplary system parameters.
[0045] Referring to FIG. 2, the transmission element 14 may include a waveguide or optical fiber 18 that directs light or another type of signal (e.g., acoustic energy) along a curved or bent path. The optical fiber 18 may include one or more fibers made of glass (e.g., silica, fluorozirconate, fluoroaluminate, and chalcogenide), crystalline materials (e.g., sapphire), and/or plastic. In one embodiment, the optical fiber 18 is a rigid fused glass fiber. The optical fiber 18 may be flexible.
[0046] Referring to FIG. 3, in some embodiments, the transmission element 14 includes a reflective surface 20 that reflects the signal from the emitter 12 to the detector 16. The reflective surface 20 may be any type of reflective surface, such as a mirror, a diffuser, and/or a light colored surface (e.g., a diffuse plastic, such as white acetal). The reflective surface 20 is preferably used when the emitter 12 and detector 16 are in close proximity with one another. For example, the reflective surface 20 may be positioned in front of a sensor that includes both the emitter 12 and the detector 16 (e.g., a fluorometer).
[0047] In certain embodiments, referring to FIG. 4, a system 40 for assessing sensor degradation includes a sensor 42 exposed to a surrounding environment, a reference emitter 44 protected from the environment, and a reference detector 46 also protected from the environment. The sensor 42 includes a sensor emitter 48 that may be similar to or a duplicate of the reference emitter 44. The sensor 42 also includes a sensor detector 50 that may be similar to or a duplicate of the reference detector 46. Each of the detectors in the system is configured to receive a signal from each of the emitters. For example, the sensor detector 50 is configured to receive a signal 51 from the sensor emitter 48 via transmission element 52 or a signal 53 from the reference emitter 44 via transmission element 54. Likewise, the reference detector 46 is configured to receive a signal 55 from the sensor emitter 48 via transmission element 56 or a signal 57 from the reference emitter 44 via transmission element 58.
[0048] Use of the protected reference emitter 44 and reference detector 46 allows the sensor 42 to be assessed for degradation. For example, to assess the degradation of the sensor detector 50, the reference detector 46 may periodically receive the signal 55 (e.g., a calibration signal) from the sensor emitter 48 via transmission element 56. The signal 55 may then be compared to the signal 51 received by the sensor detector 50 from the sensor emitter 48 via transmission element 52. Differences between the two signals may be used to assess the degradation of the sensor detector 50 due to exposure in the surrounding environment. The sensor detector 50 may be recalibrated or adjusted accordingly to compensate for the degradation.
[0049] Likewise, to assess the degradation of the sensor emitter 48, the reference emitter 44 may periodically transmit the signal 53 (e.g., a calibration signal) to the sensor detector 50 via transmission element 54. The signal 53 may then be compared to the signal 51 received by the sensor detector 50 from the sensor emitter 48 via transmission element 52. Differences between the two signals may be used to assess the degradation of the sensor emitter 48 due to exposure in the surrounding environment. Any necessary adjustments to sensor measurements may be made accordingly.
[0050] In some embodiments, the reference emitter 44 and/or the reference detector 46 may be assessed for degradation by periodically sending the signal 57 from the reference emitter 44 to the reference detector 46 via transmission element 58. The signal 57 may be compared with one or more previous signals transmitted from the reference emitter 44 to the reference detector 46 to identify any differences (e.g., in signal intensity or frequency content) between the signal 57 and the previous signal(s). Such differences may be indicative of degradation, and the system 40 may adjust measurements or sensor output accordingly. [0051] To protect the reference emitter 44 and the reference detector 46 from the surrounding environment, the reference emitter 44 and the reference detector 46 may be covered by or enclosed within at least one protective member 60. The protective member 60 may include, for example, a sealed container, a surface treatment or coating, a solid barrier, a movable shutter or barrier, an anti-fouling material, and a toxic material. Alternatively or additionally, the reference emitter 44 and/or the reference detector 46 may be periodically cleaned or scrubbed (e.g., with a brush, mechanical action, and/or UV light) to remove or reduce any degradation.
[0052] Although the system 40 is depicted as including both the reference emitter 44 and the reference detector 46, in alternative embodiments one or both of these reference elements may not be included. For example, in the embodiment depicted in FIG. 5, a system 62 for assessing sensor degradation does not include a sensor emitter and therefore may not need a reference detector (e.g., to assess the degradation of the sensor emitter). The system 62 in this case may include the reference emitter 44 for sending the signal 53 to the sensor detector 50 via transmission element 54. Likewise, in the embodiment depicted in FIG. 6, a system 64 for assessing sensor degradation does not include a sensor detector and therefore may not need a reference emitter (e.g., to assess the degradation of the sensor detector). The system 64 in this case may include the reference detector 46 for receiving the signal 55 from the sensor emitter 48 via transmission element 56.
[0053] In various embodiments, the systems and methods described herein are used to assess and/or compensate for degradation associated with a sensor. A signal from an emitter to a detector may be used to detect sensor degradation, and output from the sensor (e.g., a voltage or sampled numerical values) may be adjusted or calibrated to compensate for the degradation. In some embodiments, the emitter and/or the detector form at least part of the sensor. For example, the detector may be disposed within the sensor and the emitter may be outside the sensor but configured to send a signal (e.g., acoustic energy or light) to the detector.
Alternatively, the emitter and the detector may not form part of the sensor. For example, the sensor may not include the detector and may not receive a signal from the emitter. In that case, a signal from the emitter to the detector may be used to determine an amount of degradation associated with or in the vicinity of the emitter and the detector and, based on that amount, adjust an output from the sensor accordingly. In that case, a relationship between sensor performance and the degradation associated with the emitter and the detector may have been previously determined (e.g., in the form of look-up tables or calibration curves).
[0054] FIG. 7 depicts an aquatic optical device 70 for performing optical measurements in an aquatic environment, in accordance with certain embodiments of the invention. The optical device 70 includes a fluorometer 72 (e.g., a custom WET LABS FLBBCD fluorescence sensor) and a photosynthetically active radiation (PAR) sensor 74 (e.g., a SATLANTIC PAR-LOG- 2000m irradiance sensor). The optical device 70 also includes a sensor 76 for measuring salinity, temperature, pressure, and/or dissolved oxygen (e.g., a SEABIRD SBE41CP CTD sensor with an integrated DO sensor). The optical device 70 may be used to perform various optical measurements, including fluorescence due to CDOM, chlorophyll, phycoerythrin, phycocyanin, rhodamine fluorescence, and uranine. As depicted, the optical device 70 includes a shutter 78 and an actuator 80. The actuator 80 may be used to cycle the shutter 78 between an open position (in which the sensors are uncovered) and a closed position (in which the sensors are covered). In general, the shutter 78 is configured to cover and protect the sensors when aquatic measurements are not being performed. The specific embodiment depicted in FIG. 7 is an ITP autonomous observing system.
[0055] The shutter 78 may include or consist of a fouling-resistant material or have a fouling resistant surface. For example, the shutter 78 may be made of a naturally toxic material, such as copper or silver, and/or may include a fouling-resistant coating. In one example, the shutter 78 is made of plastic and is coated with a biofouling paint. The actuator 80 may be, for example, a SATLANTIC BIO SHUTTER actuator.
[0056] Referring to FIG. 8, in various embodiments, the transmission element 14 of the aquatic optical device 70 is attached to the shutter 78. Actuation of the shutter 78 may cycle the transmission element 14 between the active and inactive positions. For example, when the shutter 78 is closed, the transmission element 14 may be in the active position, for directing light from the light source (e.g., the fluorometer 72) to the light detector (e.g., the PAR sensor 74). In the depicted embodiment, the transmission element 14 is a U-shaped, potted optical fiber. Alternatively or additionally, the transmission element 14 may be or may include a reflective surface. For example, a bottom surface of the shutter 78 (i.e., the surface that faces the sensors) may include a mirror or white acetal to reflect light from the light source to the light detector. [0057] Advantageously, the aquatic optical device 70 allows the degree of biofouling accumulation to be monitored and assessed over time. As biofouling accumulates on the aquatic optical device 70, data collected by the sensors may be adjusted and/or validated, as needed, based on the biofouling assessment. In one embodiment, an initial calibration of the emitter 12, the transmission element 14, and the detector 16 is performed in clean water with clean surfaces, before the optical device 70 has been deployed in an aquatic environment.
[0058] In general, biofouling reduces the amount of light transmitted from the emitter 12 to the detector 16. By determining the reduction in light transmission, optical data from one or more sensors on the optical device 70 may be corrected accordingly. For example, if the biofouling is found to reduce the amount of light received by the detector 16 by ten percent, light intensity values received by a sensor during aquatic measurements may be corrected by ten percent, to compensate for the biofouling. As mentioned, optical data collected by the sensors may also be adjusted based on changes in the frequency spectrum of the detected light, due to the biofouling. To adjust the optical data, a sensor gain and/or a sensor bias may be adjusted, as desired.
[0059] In some embodiments, the shutter 78 includes a cleaning device (e.g., a brush or a blade) for reducing the accumulation of biofouling on the aquatic optical device 70. The cleaning device may be attached to the bottom surface of the shutter 78. When the shutter 78 is opened and/or closed, the cleaning device may scrub or wipe a sensor (e.g., an optical face of the sensor), the emitter 12, and/or the detector 16. Cleaning the emitter 12 and/or the detector 16 in addition to the sensor may keep the biofouling consistent among the sensor, the emitter 12, and/or the detector 16. In one embodiment, rather than simply cycling between the open and closed positions, the shutter 78 actuates to a third position (i.e., a cleaning position) to allow the brush (or other cleaning device) to perform the cleaning function. Use of the cleaning device may prolong the usable life of the aquatic optical device and/or improve measurement accuracy.
[0060] In various embodiments, the biofouling assessment system 10 is used as a biofouling sensor to measure the biofouling process itself, rather than or in addition to assessing biofouling for the purpose of adjusting data collected by an optical sensor. For example, the emitter 12 and the detector 16 may be used to measure the amount of biofouling that occurs over time, as a function of the frequency of cleaning (e.g., once per day or once per month) and/or other cleaning parameters, such as the type of brush and the speed of the brush. The biofouling assessment system 10 may also be used to assess biofouling rates in different regions of the ocean, for example, as a function of environmental parameters, such as salinity, temperature, pressure, biological productivity, and/or dissolved oxygen. The biofouling assessment system 10 may therefore act as a biofouling meter, suitable for long-term autonomous deployments.
[0061] Some sensors, such as a radiometer or a PAR irradiance sensor, generally require the optical face of the sensor to remain unblocked or uncovered for extended periods of time, as measurements are performed. For such sensors, it may be desirable to maintain the biofouling assessment system 10 in the inactive position most of the time (e.g., more than 90% of the time) and in the active position only for brief, intermittent periods of time. Because a shutter would be open most of the time for these sensors, and would therefore do little to prevent biofouling, the shutter 78 may not be needed for these sensors. Accordingly, the biofouling assessment system 10 may be mounted to one or more other components of the optical device 70 (i.e., instead of the shutter 78), which may or may not be actuated. In one embodiment, the emitter 12, the detector 16, and the transmission element 14 are housed within a common housing.
[0062] In various embodiments, the emitter 12 and/or the detector 16 are configured to be moved into position with respect to one or more sensors on the aquatic optical device 12. For example, the emitter 12 and/or the detector 16 may be attached to the shutter 78, and the shutter 78 may move the emitter 12 and/or the detector 16 in front of a sensor. In this instance, the transmission element 14 may be the fluid (e.g., water) between the shutter 78 and the sensor. Specifically, light from a sensor may pass through the fluid to the detector 16, and/or light from the emitter 12 may pass through the fluid to the sensor.
[0063] In some implementations, the aquatic optical device includes more than one transmission element 14. For example, a first transmission element 14 may include an optical fiber, and a second transmission element 14 may include a reflective surface, such as a diffuser or mirror. The transmission elements 14 may be attached to the shutter 78 or other actuation device, which may be cycled among multiple positions. For example, the shutter 78 may have a fully open position in which no transmission element 14 is in front of a sensor. The shutter may also have a first position in which the first transmission element 14 is in front of a sensor, and a second position in which the second transmission element 14 is in front of the same or different sensor. The transmission elements 14 may be in their active positions simultaneously, or at different times. Any combination of transmission elements 14, light sources 12, light detectors 16, and/or cleaning devices may be incorporated onto the shutter 78, and the shutter 78 may be actuated to multiple positions to achieve the desired placement of each component.
[0064] As mentioned, the emitter 12 and/or the detector 16 may be integrated into one or more optical sensors, such as a fluorometer and/or a PAR sensor. Alternatively or additionally, the emitter 12 and/or the detector 16 may not be integrated into one or more optical sensors and may have no other purpose than to assess the amount of biofouling that has occurred on the aquatic optical device 70. For example, a custom light detector (i.e., a light detector that is not integrated into a sensor) may be used to detect light from a custom light source (i.e., a light source that is not integrated into a sensor). Additionally, a custom light detector may be used to detect light from a sensor (e.g., a fluorometer), a custom light source may be used to provide light to a sensor (e.g., a PAR sensor), and/or a pair of sensors (e.g., a PAR sensor and a fluorometer) may be coupled with a custom light source and custom light detector. Biofouling may be assessed continually or intermittently (e.g., only when the shutter is closed), using the biofouling assessment system.
[0065] The devices and methods described herein, including aquatic optical device 70, may be utilized in any aquatic environment. For example, the devices and methods may be used in salt water, fresh water, the ocean, a lake, a river, a pond, an aquifer, a drinking water supply, a pipeline, a swimming pool, or any other body of water. References to "ocean,"
"oceanographic," and like are not to be interpreted as limiting the devices and methods to use only in the ocean and/or an oceanographic context.
[0066] The devices and methods described herein may be used with any type of optical sensor. The optical sensor may be for measuring biological properties, and/or the optical sensor may be for measuring non-biological properties. The optical sensor may be or may include, for example, a fluorometer, a radiometer, a PAR sensor, and/or a dissolved oxygen sensor.
[0067] Each numerical value presented herein, for example, in a table, a chart, or a graph, is contemplated to represent a minimum value or a maximum value in a range for a corresponding parameter. Accordingly, when added to the claims, the numerical value provides express support for claiming the range, which may lie above or below the numerical value, in accordance with the teachings herein. Absent inclusion in the claims, each numerical value presented herein is not to be considered limiting in any regard. [0068] The terms and expressions employed herein are used as terms and expressions of description and not of limitation, and there is no intention, in the use of such terms and expressions, of excluding any equivalents of the features shown and described or portions thereof. In addition, having described certain embodiments of the invention, it will be apparent to those of ordinary skill in the art that other embodiments incorporating the concepts disclosed herein may be used without departing from the spirit and scope of the invention. The features and functions of the various embodiments may be arranged in various combinations and permutations, and all are considered to be within the scope of the disclosed invention.
Accordingly, the described embodiments are to be considered in all respects as only illustrative and not restrictive. Furthermore, the configurations, materials, and dimensions described herein are intended as illustrative and in no way limiting. Similarly, although physical explanations have been provided for explanatory purposes, there is no intent to be bound by any particular theory or mechanism, or to limit the claims in accordance therewith.
[0069] What is claimed is:

Claims

Claims
1. A sensor assessment system comprising:
an emitter;
a detector;
a transmission element for directing a signal from the emitter to the detector; and a processor for adjusting output of a sensor based on the signal to compensate for degradation of the sensor caused by exposure to a surrounding environment,
wherein at least one of the emitter and the detector is exposed to the surrounding environment.
2. The system according to claim 1, wherein:
the emitter comprises a light source;
the detector comprises a light detector;
the transmission element comprises an optical transmission element for directing light from the light source to the light detector; and
the degradation comprises biofouling.
3. The system according to claim 2, wherein the sensor comprises the light detector.
4. The system according to claim 2, wherein the light source comprises a module with an integral light source.
5. The system according to claim 4, wherein the light source module is selected from the group consisting of fluorometers, scattering meters, transmissometers, and non-sensing light generators.
6. The system according to claim 2, wherein the light detector is selected from the group consisting of radiometers, fluorometers, transmissometers, scattering meters, and dedicated light detectors.
7. The system according to claim 2, wherein the optical transmission element comprises a first end disposed proximate the light source and a second end disposed proximate the light detector.
8. The system according to claim 2, wherein the optical transmission element is selected from the group consisting of an optical fiber, a mirror, a gas, a liquid, an optically diffusing material and combinations thereof.
9. The system according to claim 2 further comprising an element moveable between a first position covering the sensor and a second position uncovering the sensor.
10. The system according to claim 9, wherein the optical transmission element is disposed on the moveable element.
1 1. The system according to claim 9, wherein the moveable element is selected from the group consisting of shutters, brushes, biofouling minimization treated components, and combinations thereof.
12. The system according to claim 9, wherein the moveable element comprises at least one of copper, another biofouling resistant material, a material treated with a bioresistant coating, and combinations thereof.
13. The system according to claim 9, further comprising an actuator to move at least one of the optical transmission element and the moveable element between the first position and the second position.
14. The system according to claim 2, further comprising a control adapted to trend sensor output over time corresponding at least in part to a degree of biofouling of the sensor.
15. The system according to claim 14, wherein the control is further adapted to apply a correction factor to sensor output, based on the degree of biofouling.
16. A method of assessing degradation of a sensor, the method comprising the steps of: sending an initial signal from an emitter toward a sensor subject to degradation when the sensor is in a clean condition, the sensor comprising an integral detector;
detecting the initial signal with the integral detector and optionally storing an output of the clean condition sensor;
thereafter periodically sending a calibration signal from the emitter toward the sensor; and
adjusting an output of the sensor based on the calibration signal to compensate for degradation of the sensor caused by exposure to a surrounding environment.
17. The method of claim 16, wherein:
the emitter comprises a light source;
the degradation comprises biofouling; and
the integral detector comprises an optical light detector.
18. The method according to claim 17, further comprising the step applying a correction factor to sensor output, based on the degree of biofouling.
19. The method according to claim 17, wherein the light source comprises a module with an integral light source.
20. The method according to claim 19, wherein the light source module is selected from the group consisting of fluorometers, scattering meters, transmissometers, and non-sensing light generators.
21. The method according to claim 17, wherein the sensor is selected from the group consisting of radiometers, fluorometers, transmissometers, scattering meters, and dedicated light detectors.
22. The method according to claim 17, wherein at least one directing step uses an optical transmission element disposed between the light source and the optical detector of the sensor.
23. The method according to claim 22, wherein the optical transmission element comprises a first end disposed proximate the light source and a second end disposed proximate the optical detector of the sensor.
24. The method according to claim 22 further comprising the step of moving an element between a first position covering the sensor and a second position uncovering the sensor.
25. The method according to claim 24, wherein the optical transmission element is disposed on the moveable element.
26. The method according to claim 24, wherein the moveable element is selected from the group consisting of shutters, brushes, biofouling minimization treated components, and combinations thereof.
27. The method according to claim 22, wherein the optical transmission element is selected from the group consisting of an optical fiber, a mirror, a gas, a liquid, an optically diffusing material and combinations thereof.
28. The method according to claim 24, wherein the moveable element comprises at least one of copper, another biofouling resistant material, a material treated with a bioresistant coating, and combinations thereof.
29. The method according to claim 24 further comprising the step of energizing an actuator to move at least one of the optical transmission element and the moveable element between the first position and the second position.
30. A sensor assessment system comprising:
a sensor comprising a detector exposed to a surrounding environment;
a reference emitter protected from the surrounding environment;
a transmission element for directing a signal from the reference emitter to the detector; and a processor for adjusting output of the sensor based on the signal to compensate for degradation of the sensor caused by exposure to the surrounding environment.
31. The system of claim 30, wherein the degradation is selected from the group consisting of biofouling, dirt accumulation, salt coating, precipitate coating, extraction of plasticizers, sensor surface scratching, sensor surface cracking, corrosion, rust, liquid permeation, gas permeation, and salt permeation.
32. The system of claim 30, wherein the signal is selected from the group consisting of an acoustic signal, a thermal signal, a radio wave signal, a microwave signal, an infrared signal, a visible light signal, an ultraviolet light signal, an x-ray signal, and an electrical signal.
33. The system of claim 30, wherein:
the sensor further comprises an emitter exposed to the surrounding environment;
the system further comprises (i) a reference detector protected from the surrounding environment, and (ii) a second transmission element for directing a second signal from the emitter to the reference detector; and
the processor is for adjusting output of the sensor based on the second signal to compensate for degradation of the sensor caused by exposure to the surrounding environment.
34. A method of assessing degradation of a sensor, the method comprising the steps of: sending a first signal from an emitter to a detector, the emitter and the detector forming at least part of a sensor exposed to a surrounding environment;
sending a second signal from a reference emitter to the detector, the reference emitter being protected from the surrounding environment;
comparing the first signal with the second signal; and
based on the comparison, adjusting an output from the sensor to compensate for degradation of the sensor caused by exposure to the surrounding environment.
35. The method of claim 34, wherein the degradation is selected from the group consisting of biofouling, dirt accumulation, salt coating, precipitate coating, extraction of plasticizers, sensor surface scratching, sensor surface cracking, corrosion, rust, liquid permeation, gas permeation, and salt permeation.
36. The method of claim 34, wherein the first signal and the second signal are each independently selected from the group consisting of an acoustic signal, a thermal signal, a radio wave signal, a microwave signal, an infrared signal, a visible light signal, an ultraviolet light signal, an x-ray signal, and an electrical signal.
PCT/US2013/057951 2012-09-04 2013-09-04 Sensor degradation assessment and correction system WO2014039496A2 (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9988242B1 (en) 2017-01-11 2018-06-05 Otis Elevator Company Elevator rail healthy monitoring method
US11679423B2 (en) 2016-03-31 2023-06-20 Koninklijke Philips N.V. Integrated system for real-time anti-fouling and biofouling monitoring

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7095500B2 (en) * 2004-01-30 2006-08-22 Nalco Company Interchangeable tip-open cell fluorometer
ATE495433T1 (en) * 2007-03-24 2011-01-15 Sick Engineering Gmbh POLLUTION MEASUREMENT
DE102009028254A1 (en) * 2009-04-22 2010-10-28 Endress + Hauser Conducta Gesellschaft für Mess- und Regeltechnik mbH + Co. KG Method for investigations on liquids and device therefor

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
None

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US11679423B2 (en) 2016-03-31 2023-06-20 Koninklijke Philips N.V. Integrated system for real-time anti-fouling and biofouling monitoring
US9988242B1 (en) 2017-01-11 2018-06-05 Otis Elevator Company Elevator rail healthy monitoring method

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