A spatiotemporal measurement system and method for field subjects using an optical web.

Abstract

The present invention provides novel and advantageous systems and methods for measuring atmospheric substances (e.g., greenhouse gases such as nitrous oxide (N2O)) in the field (e.g., in agricultural environments) or in other areas. [Solution] The present invention provides a system and method for measuring atmospheric substances (e.g., greenhouse gases such as nitrous oxide) in a field or other area. An optical web can be projected onto the field using lasers supplied from two or more towers positioned around the edge of the field, thereby estimating flux emissions and their spatiotemporal parameters. Each laser is configured to supply light of a predetermined wavelength to one or more reflectors positioned around the edge of the field, thereby measuring a path integral, which is then returned from the reflectors to a detector positioned coaxially with each laser. By performing numerous such measurements, a set of linear equations can be generated, which can be used to calculate emissions in any single grid cell of the field.

Description

Technical Field

[0001] The present invention relates to a spatio-temporal measurement system and method for a subject on a field using an optical web.

[0002] [Government Support] The present invention was made with government support under grant number DE-AR0001385 awarded by the Department of Energy. The government has certain rights in the present invention.

Background Art

[0003] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 523,690, filed Jun. 28, 2023, and U.S. Provisional Patent Application No. 63 / 631,904, filed Apr. 9, 2024, and the entire disclosure thereof, including all figures, tables, and drawings, is incorporated herein by reference.

[0004] In agriculture, many greenhouse gases and air pollutants are generated, which may have an adverse impact on the environment. Therefore, before reporting obligations come into effect, before mitigation measures are implemented, or before claims regarding environmental sustainability can be made, the government has imposed restrictions on the emissions from specific farms or fields. If the generation amount of specific emissions can be minimized or reduced, products with a low environmental impact can be sold in the carbon credit market, bringing benefits to the owners of farms or fields that have fallen below the emission limits. Such efforts can also be monetized through marketing that claims the environmental sustainability of products. Therefore, it is important to accurately measure the emissions of greenhouse gases and air pollutants resulting from agricultural activities.

Summary of the Invention

Problems to be Solved by the Invention

[0005] Embodiments of the present invention provide novel and advantageous systems and methods for measuring atmospheric subjects (e.g., greenhouse gases such as nitrous oxide (N2O)) in a field (e.g., a field in an agricultural environment) or other area. An optical web can be projected onto the field or other area using light sources (e.g., lasers) positioned or installed on towers or platforms monitoring the field or other area, along with meteorological data of wind speed. Flux emissions and spatiotemporal parameters can be estimated by two or more towers positioned around the edge (e.g., just outside) of the field or other area. Each light source can be configured to supply light of a predetermined wavelength (e.g., mid-infrared (mid-IR) wavelength) to one or more reflectors (e.g., retroreflectors) positioned around the edge (e.g., just outside) of the field or other area to measure path integrals, the light then returning from the reflectors to detectors positioned coaxially with each light source. A "grid cell" is calculated from overlapping rays (e.g., laser beams) on the field (or other area) based on the density and / or arrangement of the reflectors. By performing numerous such measurements, a series of linear equations can be generated, which can be used to calculate emissions in any single grid cell of the field (or other region) described above. This information can be combined with meteorological data in an atmospheric inversion model to estimate the final emissions (or subject concentrations). [Means for solving the problem]

[0006] In one embodiment, a system for measuring at least one subject in the atmosphere over a field (e.g., farmland) may comprise at least two towers positioned on or near the boundary of the field, each equipped with at least one mid-infrared (mid-IR) light source (e.g., a laser) configured to supply light of a predetermined wavelength to a specific subject, the predetermined wavelength being in the range of 2 micrometers (μm) to 30 μm; a plurality of reflectors positioned around the boundary of the field and configured to reflect light from the mid-IR light source of each of the at least two towers; and an analysis unit operably communicating with the at least one mid-IR light source of each of the at least two towers. Each of the at least two towers may further comprise a detector (e.g., a mercury-cadmium-tellurium (MCT) detector and / or image sensor) configured to receive signals of light reflected from the plurality of reflectors. The system may further include a weather station that operably communicates with the analysis unit, and the weather station may be configured to acquire weather data of the atmosphere on the field, the atmosphere adjacent to the field, or both. The weather data may include, for example, wind speed, wind direction, atmospheric pressure, temperature, humidity, or a combination thereof. The weather station may be located within or adjacent to the field. Each of the at least one subject may be, for example, a greenhouse gas (e.g., N2O, ammonia (NH3), methane (CH4), carbon dioxide (CO2), ozone (O3), or a combination thereof). The system may be configured to measure each of the at least one subject with an accuracy of about 1 / 1000th of the environmental level (i.e., background level) of each gas in the atmosphere away from nearby sources. This is on the order of parts per billion (ppb) or less (e.g., 100 ppb for CO2, 0.1 ppb for N2O, 0.1 ppb for NH3, 0.1 ppb for O3).The system described above may be configured to measure the at least one subject with a sensitivity / accuracy of 100 ppb or less, 10 ppb or less, 1 ppb or less, 0.1 ppb or less, 1 ppb, approximately 1 ppb, 0.1 ppb, or approximately 0.1 ppb. The plurality of reflectors may be arranged at equal intervals around the boundary of the field and / or in close proximity to each other around the boundary of the field, and the analysis unit generates a map of the concentration of the at least one subject at a predetermined particle size. The analysis unit may store software configured to receive the signals of light reflected from the plurality of reflectors and convert them into data indicating the concentration of the at least one subject in the atmosphere. The analysis unit may convert the signals by wavelength modulation spectroscopy, direct absorption spectroscopy, or both. The data indicating the concentration of the at least one subject in the air may include at least one of spatial information of the concentration of the at least one subject in the air, vertical profile information of the concentration of the at least one subject in the air, and flux of the concentration of the at least one subject in the air. The system may further include a display that operably communicates with the analysis unit, the analysis unit may be configured to display the data indicating the concentration of the at least one subject in the air on the display. Each of the plurality of reflectors may be, for example, a retroreflector configured to reflect medium IR light. The retroreflector may include a base substrate and a coating layer disposed on the base substrate. The base layer may include a thermoplastic material (e.g., a polymer such as polymethyl methacrylate (PMMA)). The coating layer may include a metal (e.g., aluminum (Al), gold (Au), silver (Ag), or a combination thereof). The thickness of the coating layer may be, for example, 10,000 angstroms or less (e.g., 5,000 angstroms or less, such as 2,500 angstroms or about 2,500 angstroms). The retroreflector may further include an adhesive layer disposed between the base substrate and the coating layer, and / or a protective layer disposed on the coating layer.The adhesive layer may contain a transition metal (e.g., titanium (Ti), chromium (Cr), or a combination thereof). The thickness of the adhesive layer may be, for example, 10,000 angstroms or less (e.g., 5,000 angstroms or less, such as 500 angstroms or about 500 angstroms). The protective layer may contain an insulating material (e.g., silicon oxide). The total thickness of the retroreflector may be 50 millimeters (mm) or less (e.g., 25 mm or less, 10 mm or less, 4 mm or less, about 4 mm, or 4 mm). The at least two towers may include two towers arranged symmetrically to each other on opposite sides of the field. The analysis unit may include an FPGA such as a custom field-programmable gate array (FPGA). Each of the at least two towers may further include a visible light source (e.g., a visible light laser) configured to supply visible wavelength light to facilitate alignment during initial setup. Each of the at least two towers described above may further include a gimbal (e.g., a joystick-controlled gimbal) for directing the medium IR light (e.g., a laser beam) to each reflector in the field. The at least one medium IR light source may be, for example, light from a quantum cascade laser (QCL), an interband cascade laser (ICL), an antimonide laser, a lead salt laser, a light-emitting diode (LED), one or more frequency combs, or a difference frequency generator. At least two of the towers present may include reflectors (i.e., all towers present may include reflectors).

[0007] In other embodiments, a method for measuring at least one subject in the atmosphere over agricultural land may include: i) providing a system disclosed herein (e.g., a system having any combination of the features of the preceding paragraph); ii) transmitting medium IR light from at least one medium IR light source in the first tower of the at least two towers to the first reflector of the plurality of reflectors, and receiving reflected light from the first reflector; iii) moving the at least one medium IR light source in the first tower to transmit medium IR light from at least one medium IR light source in the first tower to the other reflectors of the plurality of reflectors, and receiving reflected light from the other reflectors; iv) repeating step iii) for each of the other reflectors of the plurality of reflectors; v) repeating steps ii) to iv) for each of the other towers of the at least two towers present, if necessary; and vi) using the analysis unit to convert the reflected light signal into data indicating the concentration of the at least one subject in the atmosphere. When each of the first tower and the second tower, which is symmetrically located opposite the first tower, directly illuminates the other, the overlapping path lengths of the light (e.g., laser beams) allow each tower's at least one medium IR light source to be internally calibrated to exactly the same optical path length. The method may further include displaying the data indicating the concentration of the at least one subject in the air on a display that operably communicates with the analysis unit. Although at least two towers are disclosed in this and the previous paragraph, a platform may be used instead of any or all of the towers. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 shows an overhead view of a farmland with a tower and reflector according to one embodiment of the present invention. The (red) lines crossing the farmland represent the path of the laser beam from the tower to the reflector and back from the reflector to the tower. [Figure 2]Figure 2 shows an image of a tower positioned at the edge of farmland according to one embodiment of the present invention. The (red) line crossing the farmland represents the path of the laser beam from the tower to the reflector and back from the reflector to the tower. The inset shows an image of an example of a reflector that can be used in an embodiment of the present invention. [Figure 3] Figure 3 shows an example of a spatial map of subject concentrations obtainable using the system and method of the embodiment of the present invention. The scale bar on the right side of Figure 3 shows the scale of the nitrous oxide (N2O) flux. [Figure 4] Figure 4 shows an image of an example of a reflector usable in an embodiment of the present invention. The scale bar is 10 millimeters (mm). [Figure 5] Figure 5 shows a schematic diagram of an optical system that can be installed in a tower according to one embodiment of the present invention. [Figure 6] Figure 6 shows images of various reflectors usable in the system of the embodiment of the present invention. Figure 6 also shows a chart of the normalized signal intensity (in arbitrary units) for various reflectors when used in the system of the embodiment of the present invention. [Figure 7] Figure 7 shows images of various reflectors that can be used in the system of the embodiment of the present invention. [Figure 8] Figure 8 shows the change in N2O concentration (in parts per billion (ppb)) against time (the upper plot is in hours, and the lower two plots are in seconds). [Figure 9] Figure 9 shows an image of the reflector and tower setup according to one embodiment of the present invention. [Figure 10] Figure 10 shows an overhead view of the field used to test a system according to one embodiment of the present invention (top) and an image of an optical system that can be placed inside a tower according to one embodiment of the present invention (bottom). [Figure 11] Figure 11 shows the change in N2O concentration (in ppb units) against time (the left plot and the top two plots show time, while the bottom two plots on the right show seconds). [Figure 12] Figure 12 is a time-space plot illustrating atmospheric mixing. [Figure 13] Figure 13 shows the calculation of the concentration of the test subject in air. [Figure 14] Figure 14 shows an example of spectroscopy. [Modes for carrying out the invention]

[0009] Embodiments of the present invention provide novel and advantageous systems and methods for measuring atmospheric subjects (e.g., greenhouse gases such as nitrous oxide (N2O)) in a field (e.g., a field in an agricultural environment) or other area. An optical web can be projected onto the field or other area using light sources (e.g., lasers) installed or positioned on towers or platforms monitoring the field or other area, along with meteorological data of wind speed. Flux emissions and spatiotemporal parameters can be estimated by two or more towers positioned around the edge (e.g., just outside) of the field or other area. Each light source can be configured to supply light of a predetermined wavelength (e.g., mid-infrared (mid-IR) wavelength) to one or more reflectors (e.g., retroreflectors) positioned around the edge (e.g., just outside) of the field or other area to measure path integrals, the light then returning from the reflectors to detectors positioned coaxially with each light source. A "grid cell" is calculated from overlapping rays (e.g., laser beams) on the field (or other area) based on the density and / or arrangement of the reflectors. By performing numerous such measurements, a series of linear equations can be generated, which can be used to calculate emissions in any one grid cell of the field (or other region) described above. This information can be combined with meteorological data in an atmospheric inversion model to estimate the final emissions (or subject concentrations), which can be done as a function of the grid cells. Each light source may be, for example, a quantum cascade laser (QCL), an interband cascade laser (ICL), an antimonide laser, a lead salt laser, a light-emitting diode (LED), one or more frequency combs, or light from a difference frequency generator. At least two of the towers present may include reflectors (i.e., all towers present may include reflectors). In many embodiments, each light source is a laser.

[0010] Conventional sensing technologies are limited to either spatial or temporal resolution. For example, measurements using drones or vehicles can produce measurements with high spatial resolution, but they cannot be operated continuously in practice. Eddy correlation and soil flux chamber methods can operate for several months or more and provide temporal resolution, but they cannot obtain spatial resolution for the entire field or other area. Flux measurements using eddy correlation cannot be performed in light winds or under conditions of high atmospheric stability and can only measure flux in the upwind direction. Flux measurements using eddy correlation cannot eliminate spatial heterogeneity within the upwind "footprint". Flux chamber methods disturb the soil in which the chamber is embedded, and analysis requires considerable effort and consumables for off-site analysis. Embodiments of the present invention provide both spatial and temporal resolution and are spatially limited only by the density of reflectors around the field or other area. The systems and methods of the embodiments provide a "gold standard" for measuring the emissions of target subjects (e.g., gases), particularly greenhouse gases such as N2O.

[0011] Embodiments of the present invention can be used for tomographic imaging of the flux of a subject (e.g., gas) in any space. While the system can be constructed and / or optimized for measurements in agricultural fields, it can also be used to measure any field, body of water, or large indoor / outdoor spaces (such as livestock farms or industrial facilities). The system and method can be used particularly for measuring greenhouse gases such as N2O, which are relevant to the carbon credit market and regulatory compliance. In some embodiments, reflectors can be mounted on drones, small radio-controlled (RC) cars or boats, surface buoys, towers, or other structures, allowing for dynamic imaging in diverse environments with a laser tower tracking the moving platform.

[0012] In a preferred embodiment, the system comprises a medium-iron reflector positioned along the field boundary and a rotating tower-based optical device including a medium-iron light source (e.g., a laser) and a detector (e.g., a mercury-cadmium-tellurium (MCT) detector and / or image sensor). The system may include one or more mirrors and / or custom field-programmable gate array (FPGA) electronics. The system may include one or more visible light lasers to assist in alignment. The gimbal position of each retroreflector may be stored by the analysis unit (or computer) for repeated exploration of each reflector. The gimbal may move the output beam on the corresponding tower to different retroreflectors. The laser may move to illuminate the next reflector after illuminating any one retroreflector for a predetermined time (e.g., a range of 1 to 10 minutes, or any sub-range within that range, such as 2 to 7 minutes). The path integral measurements from each reflector (and possibly multiple towers) can then be deconvolved into a subject concentration map of the entire region by tomography.

[0013] In many embodiments, a weather observation station (e.g., an ultrasonic anemometer or similar weather sensor) may be installed on at least one tower (which may be the same as or separate from the tower equipped with the laser) to record wind and / or other weather parameters. By combining the wind speed measurements and concentration maps using the backdiffusion method, an emissions map can be created as a function of space and time.

[0014] Figure 1 shows an overhead view image of a field having two towers and multiple reflectors according to one embodiment of the present invention. Figure 2 shows an image of a tower positioned at the edge of a field according to one embodiment of the present invention. In Figures 1 and 2, lines crossing the field represent the path of a laser beam from the tower to the reflector and back from the reflector to the tower. Referring to Figures 1 and 2, the towers can transmit light (e.g., medium-iron light) to the reflectors, which are reflected back to the respective towers and detected by detectors (e.g., MCT detectors and / or image sensors). The reflectors may be positioned outside the field (e.g., around the boundary) so that an optical web or net of the detected laser beam is generated when in use. Figure 5 shows a schematic diagram of an optical system that can be used with the towers as an example. The system may also use open-path sensing equipment or sensors (i.e., optical systems). Open-path sensing equipment or sensors means that air passively passes through the sample volume by wind or the movement of the sensing equipment / sensor (e.g., via a moving platform), and the sample volume is directly exposed to environmental conditions.

[0015] In some embodiments, the system may include an analysis unit that communicates operably with each tower. The analysis unit may be, for example, a computer storing software configured to receive signals (or reflected light from reflectors) and convert them into data indicating the concentration of the analyte in the atmosphere. The light absorption signal can be converted, for example, by wavelength modulation spectroscopy or direct absorption spectroscopy, but the embodiments are not limited thereto (see also FIG. 14 for examples of spectroscopy). The data indicating the concentration of the analyte in the atmosphere may include spatial information (e.g., the concentration in a space within the field) and / or vertical information (e.g., the concentration based on the height from the ground and in space using appropriately spaced reflectors). The data indicating the concentration of the analyte may include the flux of the analyte concentration. The analysis unit may include custom FPGA electronics. The analysis unit can communicate operably with a display capable of displaying data indicating the concentration of the analyte in the atmosphere. The display may be installed on the tower equipped with the analysis unit or may be installed at a location remote from such a tower. In the latter case, the data can be transmitted to the display via wireless or wired (e.g., buried cable). By transmitting light from the (multiple) towers towards the reflectors around the field, an overall image of the analyte concentration across the entire field can be obtained, as shown in FIG. 3.

[0016] Each laser may supply light in the mid-IR range (i.e., from 2 micrometers (μm) to 30 μm) and be configured to supply light of a specific wavelength to a particular subject. That is, each tower may include at least one laser, which may include a first laser configured to supply light of a first mid-IR wavelength for acquiring the concentration of a first subject, a second laser configured to supply light of a second mid-IR wavelength for acquiring the concentration of a second subject, a third laser configured to supply light of a third mid-IR wavelength for acquiring the concentration of a third subject, a fourth laser configured to supply light of a fourth mid-IR wavelength for acquiring the concentration of a fourth subject, and so on. If multiple lasers are present, only one laser is operated at a time to acquire the concentration of one subject at a time.

[0017] The reflectors may be arranged around the field in any reasonable manner. For example, the reflectors may be arranged at equal intervals around the field. They may also be arranged at uneven intervals. In a preferred embodiment, the reflectors are arranged at equal intervals around the field and are positioned close enough to generate a map of the subject concentration at the desired granularity. Figures 6 and 7 show images of examples of usable reflectors.

[0018] Each reflector may be any suitable reflector that reflects mid-IR laser light. In some embodiments, a new type of reflector that is inexpensive and effective may be used. Each reflector is a retroreflector configured for mid-IR light and may be of a type that has only been available for visible light in the prior art. The retroreflector may include a base substrate (e.g., a thermoplastic material such as a polymer (e.g., polymethyl methacrylate (PMMA))), any adhesive layer disposed on the base substrate, a coating layer disposed on the base substrate and any adhesive layer, and any protective layer disposed on the coating layer. The coating layer may be, for example, a metal such as aluminum (Al), gold (Au), silver (Ag), or a combination thereof. The thickness of the coating layer may be, for example, 10,000 angstroms or less (e.g., 5,000 angstroms or less such as 2,500 angstroms or about 2,500 angstroms). Any adhesive layer may include, for example, a transition metal (e.g., titanium (Ti), chromium (Cr), or a combination thereof). The thickness of any adhesive layer may be, for example, 10,000 angstroms or less (e.g., 5,000 angstroms or less such as 500 angstroms or about 500 angstroms). Any protective layer may include, for example, an insulating material (e.g., silicon oxide). The total thickness of the retroreflector may be, for example, 50 millimeters (mm) or less (e.g., 25 mm or less, 10 mm or less, 4 mm or less, about 4 mm, or 4 mm). FIG. 4 shows an image of such a retroreflector. Reflectors in the related art may cost thousands of dollars (US dollars), but the retroreflectors detailed herein can be effective at a cost of tens of dollars or less.

[0019] Embodiments of the present invention effectively project an optical web for estimating the flux emission rate and its spatio-temporal parameters. Path-integral measurements are realized by transmitting light from each tower to the reflector, and then the light returns from the retroreflector to a detector disposed coaxially with the laser on each tower.

[0020] Systems and methods according to embodiments of the present invention can measure sharp increases in subject concentrations above background concentrations (see also, for example, Figure 13). With this method, horizontal fluxes that may originate from adjacent farmland (e.g., wind) have already been taken into account as background, and sharp increases (and decreases) in subject concentrations compared to the background can be taken into account to identify subject hotspots (or "cold" spots, e.g., sedimentation) in the monitored field.

[0021] The subject may be a greenhouse gas or air pollutant such as nitrous oxide (N2O), ammonia (NH3), methane (CH4), or carbon dioxide (CO2). In some embodiments, the concentrations of multiple subjects in the atmosphere can be detected, and each subject may be a greenhouse gas or air pollutant (such as those described in the preamble). Figure 12 shows plots of atmospheric mixtures of many different gases.

[0022] The system and method according to the embodiment of the present invention can detect the concentration of a substance in the air at 500 parts per billion (ppb) or less, for example, with a sensitivity of 100 ppb or less, 50 ppb or less, 10 ppb or less, 1 ppb or less, 0.1 ppb or less, about 1 ppb, 1 ppb, about 0.1 ppb, or 0.1 ppb.

[0023] In many embodiments, it is important that the distance between each tower and each reflector is known. A 1-meter "deviation" in distance at a distance of 400 meters may correspond to an error of 1 / 400, or by analogy, to a detection concentration of approximately 1 ppb in 335 ppb. Therefore, the distance between each reflector and each tower can be determined by direct measurement (e.g., tape measure, laser rangefinder, etc.) or by optical derivation (the time delay between pulse emission from the light source and reception of said pulses can be converted to distance based on the speed of light. Another option is to calculate time (and thus distance) by measuring the phase difference between the emitted and received light). The distance between each tower and each reflector should be determined with an accuracy of 1 / 1000 (i.e., an error of no more than 0.1% of the actual distance). It is also possible to determine and determine the distance by using robust tower and / or reflector mounts.

[0024] In some embodiments, a beam splitter and / or beam expander may be provided on at least one tower. A wider beam width makes alignment easier. However, if the beam width is too wide, the amount of light reflected by the sensor becomes very small, increasing noise and reducing the accuracy of measuring the concentration of the sample.

[0025] In some embodiments, the system may include a reference cell for line locking and calibration (e.g., located in or on at least one tower), where a portion of the output beam (e.g., 5% or about 5%) is directed by a beam splitter to a reference cell containing the target gas (e.g., N2O). The light that has passed through the reference cell is then focused to a medium-iron detector. The reference cell may include a reference detector, which can be used as an absolute concentration reference, or to line lock a light source (e.g., a laser) to the absorption line of the target. Such line locking can be important in high-precision, high-stability measurements, and also in situations where the optical system is covered with water droplets during rainfall and little or no light returns from the reflector.

[0026] In some embodiments, some or all of the reflectors and / or at least one of the towers may be provided with a hood (e.g., a short hood) to minimize the impact of rainfall on measurements. This hood may be, for example, a small umbrella covering the outgoing / returning beams and reflectors. This can increase the robustness of the system.

[0027] In some embodiments, vertical profile information of the subject can be obtained by positioning the reflector perpendicular to the tower itself (for example, within the canopy of crops in the field, or above the canopy if the reflector is installed on a pole extending above the canopy). This data can be important in accurate flux measurement because the concentration profile contributes to determining the flux along with wind speed (predictability increases with altitude).

[0028] The methods and processes described herein may be embodied as code and / or data. The software code and data described herein may be stored in one or more machine-readable media (e.g., computer-readable media). This may include any device or medium capable of storing code and / or data for use by a computer system. When a computer system and / or processor reads and executes code and / or data stored in a computer-readable media, the computer system and / or processor executes the methods and processes embodied as data structures and code stored in the computer-readable storage medium.

[0029] Those skilled in the art should understand that computer-readable media include removable and non-removable structures / devices that can be used to store information such as computer-readable instructions, data structures, program modules, and other data used in computing systems / environments. Computer-readable media include, but are not limited to, volatile memory such as random access memory (RAM, DRAM, SRAM); non-volatile memory such as flash memory, various read-only memories (ROM, PROM, EPROM, EEPROM), magnetic and ferromagnetic / ferroelectric memories (MRAM, FeRAM), magnetic and optical storage devices (hard drives, magnetic tapes, CDs, DVDs); network devices; or other media currently known or to be developed that can store computer-readable information / data. Computer-readable media should not be construed as containing propagated signals. The computer-readable media in embodiments of the present invention may be, for example, a compact disc (CD), a digital video disc (DVD), a flash memory device, volatile memory, or a hard disk drive (HDD) (such as an external HDD or a computing device HDD), but the embodiments are not limited to these. The computing device may be, for example, a laptop computer, a desktop computer, a server, a mobile phone, or a tablet, but the embodiment is not limited to these.

[0030] Where ranges are used herein, combinations and partial combinations of ranges (e.g., any partial range within the disclosed range) and specific embodiments within them are expressly intended to be included. Where the term “about” is used herein with a numerical value, it is understood that the value may be within a range of 95% to 105% of the value, i.e., within ±5% of the stated value. For example, “about 1 kg” means between 0.95 kg and 1.05 kg.

[0031] To gain a deeper understanding of the embodiments of the present invention and its many advantages, the following examples are provided. The following examples illustrate some methods, uses, embodiments, and variations of the present invention. Naturally, these do not limit the present invention. Various changes and modifications are possible with respect to embodiments of the present invention.

[0032] (Example 1) A tower system was developed to perform laser scans across an entire field with inexpensive reflectors, effectively creating an optical network over the field. An image of the system is shown in Figure 1. Combining tomographic reconstruction of the laser scans with meteorological data and atmospheric inversion models enabled the creation of continuous (30-minute) and high-resolution (less than 1 acre) maps of N2O emissions. A QCL, positioned coaxially with the visible diode laser and MCT detector, was aligned with the first retroreflector. The system then rotated towards the other retroreflectors, remaining at each reflector for several minutes to complete the scan of the entire field. The entire system used two towers, maintaining self-calibration while one tower was aligned with the other, to perform a symmetrical and complete scan of the field. Custom FPGA electronics controlled the laser, detector, and all signal and data processing, achieving low power consumption suitable for field deployment. Integrated path length measurements of N2O were performed over a 400-meter round-trip path, and the results are shown in Figure 3.

[0033] (Example 2) The tower system of Example 1 was tested with a corner cube array type retroreflector using the equipment and field shown in Figure 9. The results are shown in Figure 8, demonstrating that the system is effective for measuring long-distance paths (distance of 400 meters between the tower and the reflector).

[0034] (Example 3) The system using the open-path optical sensor shown in the lower part of Figure 10 (and the schematic diagram in Figure 5) was tested on the field shown in Figure 10 using a 4x4 array of plastic retroreflectors (spaced approximately 10 meters apart). In this example, the reflectors were placed closer to the sensor than in Example 2 (for example, the round-trip distance of the reflectors indicated by the "retroreflector" arrow in Figure 10 is 98 meters). The results are shown in Figure 11, confirming that the system functioned with high accuracy as intended.

[0035] The examples and embodiments described herein are for illustrative purposes only, and it should be understood that various modifications and changes thereto will be suggested to those skilled in the art and will fall within the spirit and scope of this application.

[0036] All patents, patent applications, provisional applications, and published documents referenced or cited herein, including all figures and tables, are incorporated herein by reference in their entirety, to the extent that they do not conflict with the express teachings herein.

Claims

1. A system for measuring at least one subject in the air in a field, A first tower and a second tower, respectively, are positioned on or near the boundary of the field, each comprising at least one mid-infrared (mid-IR) light source configured to supply light of a predetermined wavelength to a specific subject, wherein the predetermined wavelength is in the range of 2 micrometers (μm) to 30 μm. A plurality of reflectors arranged around the boundary of the field and configured to reflect light from the medium IR light source of the first tower and the second tower, An analysis unit that operably communicates with the at least one medium IR light source in each of the at least one towers A system that is equipped with [the following].

2. The system according to claim 1, Each of the first tower and the second tower further comprises a first detector configured to receive signals of light reflected from the plurality of reflectors. system.

3. A system according to any one of claims 1 to 2, further, The system comprises a weather observation station that can communicate operably with the aforementioned analysis unit, The weather observation station is configured to acquire weather data of the atmosphere on the field, the atmosphere adjacent to the field, or both. system.

4. The system according to claim 3, The aforementioned weather data includes wind speed, wind direction, atmospheric pressure, temperature, humidity, or a combination thereof. system.

5. The system according to claim 3, The weather observation station is located within or adjacent to the field. system.

6. The system according to claim 1, Each of the at least one subject is a greenhouse gas or an air pollutant. system.

7. The system according to claim 6, The aforementioned at least one subject is nitrous oxide (N ２ O), ammonia (NH ３ ), methane (CH ４ ), carbon dioxide (CO ２ ), or combinations thereof system.

8. The system according to claim 1, The system is configured to measure at least one of the subjects with a sensitivity of 100 parts per billion (ppb) or less. system.

9. The system according to claim 8, The system is configured to measure at least one of the subjects with a sensitivity of 10 ppb or less. system.

10. A system according to any one of claims 8 to 9, The system is configured to measure at least one of the subjects with a sensitivity of 1 ppb or less. system.

11. The system according to claim 1, The plurality of reflectors are arranged at equal intervals around the boundary of the field. system.

12. The system according to claim 1, The plurality of reflectors are arranged in close proximity to each other around the boundary of the field, and the analysis unit generates a map of the concentrations of the at least one subject at a predetermined particle size. system.

13. The system according to claim 12, The analysis unit stores software configured to receive light signals reflected from the plurality of reflectors and convert them into data indicating the concentration of the at least one subject in the atmosphere. system.

14. The system according to claim 13, The analysis unit converts the signal by wavelength modulation spectroscopy, direct absorption spectroscopy, or both. system.

15. A system according to any one of claims 13 to 14, The data indicating the concentration of the at least one subject in the atmosphere includes at least one of spatial information of the concentration of the at least one subject in the atmosphere, vertical profile information of the concentration of the at least one subject in the atmosphere, and flux information of the concentration of the at least one subject in the atmosphere. system.

16. The system according to claim 13, further, The system includes a display that can communicate with the aforementioned analysis unit in an operable manner, The analysis unit is configured to display the data indicating the concentration of the at least one subject in the air on the display. system.

17. The system according to claim 1, Each of the aforementioned plurality of reflectors is a retroreflector configured to reflect medium IR light. system.

18. The system according to claim 17, The retroreflector comprises a base substrate and a coating layer disposed on the base substrate. system.

19. The system according to claim 18, The retroreflector further comprises at least one of an adhesive layer disposed between the base substrate and the coating layer, and a protective layer disposed on the coating layer. system.

20. The system according to claim 19, The adhesive layer contains a transition metal system.

21. A system according to any one of claims 19 to 20, The thickness of the adhesive layer is 10,000 angstroms or less. system.

22. The system according to claim 19, The protective layer includes an insulating material. system.

23. The system according to claim 18, The base substrate includes a thermoplastic material. system.

24. The system according to claim 18, The coating layer contains metal system.

25. The system according to claim 24, The coating layer includes aluminum (Al), gold (Au), silver (Ag), or a combination thereof. system.

26. The system according to claim 18, The thickness of the coating layer is 10,000 angstroms or less. system.

27. The system according to claim 17, The total thickness of the retroreflector is 50 millimeters (mm) or less. system.

28. The system according to claim 27, The total thickness of the retroreflector is 10 mm or less. system.

29. The system according to claim 1, The first tower and the second tower are arranged symmetrically to each other on opposite sides of the field. system.

30. The system according to claim 1, The analysis unit includes a field-programmable gate array (FPGA). system.

31. The system according to claim 1, Each of the first tower and the second tower further comprises a visible light source configured to supply visible wavelength light. system.

32. The system according to claim 1, Each of the first tower and the second tower further comprises a gimbal. system.

33. The system according to claim 32, The gimbal is a joystick-controlled gimbal. system.

34. The system according to claim 1, The at least one of the aforementioned IR light sources is a laser. system.

35. The system according to claim 1, At least one of the first tower and the second tower further comprises a reference detector configured for line locking and calibration. system.

36. A method for measuring at least one subject in the air on a field, i) To provide the system described in claim 1, ii) Transmit medium IR light from at least one medium IR light source of the first tower to the first reflector among the plurality of reflectors, and receive reflected light from the first reflector. iii) Move the at least one medium IR light source of the first tower, transmit medium IR light from the at least one medium IR light source of the first tower to another reflector among the plurality of reflectors, and receive reflected light from the other reflector. iv) Repeat step iii) for each of the other reflectors among the plurality of reflectors, v) Repeat steps ii) to iv) for the second tower, vi) Using the analysis unit, convert the reflected light signal into data indicating the concentration of the at least one subject in the air. method.

37. The method according to claim 36, When the beams overlap between the first tower and the second tower, the first detector of the first tower and the second detector of the second tower are internally calibrated against each other. method.

38. A method according to any one of claims 36 to 37, further, The data indicating the concentration of the at least one subject in the air is displayed on a display that is operable to communicate with the analysis unit. method.

39. Base board and A coating layer disposed on the base substrate, An adhesive layer disposed between the base substrate and the coating layer, The coating layer comprises a protective layer disposed on the coating layer, The total thickness of the retroreflector is 50 millimeters (mm) or less. Retroreflector.

40. A retroreflector according to claim 39, The adhesive layer contains a transition metal Retroreflector.

41. A retroreflector according to any one of claims 39 to 40, The thickness of the adhesive layer is 10,000 angstroms or less. Retroreflector.

42. A retroreflector according to claim 39, The protective layer is an insulating material. Retroreflector.

43. The retroreflection according to claim 39, The base substrate includes a thermoplastic material. Retroreflector.

44. A retroreflector according to claim 39, The coating layer contains metal Retroreflector.

45. A retroreflector according to claim 44, The coating layer includes aluminum (Al), gold (Au), silver (Ag), or a combination thereof. Retroreflector.

46. A retroreflector according to claim 39, The thickness of the coating layer is 10,000 angstroms or less. Retroreflector.

47. A retroreflector according to claim 39, The total thickness of the retroreflector is 10 mm or less. Retroreflector.

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