JP6586683B2 - Information processing apparatus, information processing method, and program - Google Patents

Description

  The present invention relates to an information processing apparatus, an information processing method, and a program.

Recently, global warming gas such as air pollution gases and CO _2, such as SOx and NOx generated due to industrialization and urbanization, and by trace substances such as in airborne particulate matter (aerosol) including PM2.5 in urban areas The effects of air pollution and global warming have become social problems. Since the amount and composition of these air pollutants and aerosols fluctuate in time and space, monitoring them is important for countermeasures against atmospheric environmental problems.

  As a method of atmospheric observation, for example, measurement by atmospheric sampling at a fixed point can be mentioned. In recent years, differential absorption spectroscopy (DOAS) using white light such as aviation obstacle lights as a light source and a substantially horizontal optical path in the atmosphere, and multi-axis using sky light as a light source. A long optical path differential absorption method (MAX-DOAS (Multi Axis. Differential Optical Absorption Spectroscopy) method) and the like have also been proposed. For example, Patent Document 1 discloses an example of an apparatus for measuring air pollutants.

Japanese Patent Laid-Open No. 2003-83885

  On the other hand, with the existing atmospheric observation method, it is difficult to acquire information (distribution data) indicating the spatial distribution of air polluted gas and warming gas.

  Therefore, the present invention has been made in view of the above problems, and an object of the present invention is a novel and capable of acquiring information indicating the spatial distribution of air pollutant gas and warming gas. An object is to provide an improved information processing apparatus, information processing method, and program.

In order to solve the above problems, according to an aspect of the present invention, in an environment in which light is irradiated, including the components of the band to be absorbed by the target gas to be observation target is imaged at different elevation angles from each other, it is imaged An acquisition unit that acquires the first image and the second image with substantially the same time, and for each corresponding pixel between the first image and the second image, in the corresponding pixel of the first image Based on the ratio of the first spectrum indicating the intensity of the component for each wavelength in the band and the second spectrum indicating the intensity of the component for each wavelength in the band in the pixel of the second image, A first optical thickness corresponding to a pixel is calculated, and a second optical thickness based on the first optical thickness calculated for each pixel and an absorption cross section of the target gas calculated in advance. And the pixel An analysis unit for estimating the slant column density of the target gas to respond, based on the slant column density estimated for each of the pixels, and a generation unit for generating information indicating the density distribution of the target gas, said first An information processing apparatus is provided that includes a first imaging unit that captures an image and a second imaging unit that captures the second image .

  The target gas may be a gas having an absorption spectrum in an ultraviolet to near infrared band.

  The target gas may be a gas having an optical thickness fluctuation range of 0.01 or more for each wavelength.

  The target gas is nitrogen dioxide, and the first spectrum and the second spectrum may include information indicating an intensity of a component for each wavelength in at least a part of a band of 400 to 500 nm.

  The target gas is carbon dioxide, and the first spectrum and the second spectrum may include information indicating the intensity of the component for each wavelength in at least a part of the band of 1550 to 1600 nm.

  The analysis unit may calculate the second optical thickness based on the absorption cross sections of the target gas and the oxygen dimer calculated in advance.

  The analysis unit calculates a pseudo transmittance based on an assumed value of a differential slant column concentration corresponding to each of the absorption cross sections of the target gas and the oxygen dimer, and based on the pseudo transmittance, the second transmittance is calculated. The optical thickness may be calculated.

  The analysis unit sequentially changes the assumed value of the differential slant column concentration, calculates the second optical thickness based on the pseudo transmittance according to the assumed value, and calculates the pseudo thickness for each assumed value. By comparing the second optical thickness calculated based on the transmittance and the first optical thickness calculated for each pixel, the second optical thickness that substantially matches the first optical thickness. An optical thickness may be searched, and the slant column concentration of the target gas corresponding to the pixel may be estimated based on the search result of the second optical thickness.

  The light may be sunlight scattered light.

  Each of the first image and the second image may include information indicating the light intensity of each of a plurality of bands based on a spectral result of light from the subject.

  The generation unit may generate a third image as information indicating the concentration distribution of the target gas.

  An imaging unit that captures an image within an angle of view; and an optical member that switches an imaging direction of the imaging unit. The imaging unit is configured to switch the imaging direction by the optical member, whereby the first image The second image may be taken in a time division manner.

  The acquisition unit acquires a still image for each frame as the first image and the second image from each of the first moving image and the second moving image captured at different elevation angles, and the analyzing unit Calculates the first optical thickness for each corresponding pixel between the first image and the second image acquired for each frame, and calculates the first optical thickness and the second optical thickness. Based on the optical thickness, the slant column concentration of the target gas corresponding to the pixel in the frame is estimated, the generation unit based on the slant column concentration estimated for each pixel for a plurality of frames, Information indicating a change along the time series of the concentration distribution of the target gas may be generated.

In order to solve the above problem, according to another aspect of the present invention, images are captured at different elevation angles in an environment where light including a component of a band absorbed by a target gas to be observed is irradiated. Acquiring a first image and a second image with substantially the same time taken, and a processor for each corresponding pixel between the first image and the second image A first spectrum indicating the intensity of the component for each wavelength in the band in the pixel of the image and a second spectrum indicating the intensity of the component for the wavelength in the band of the pixel of the second image Based on the ratio, the first optical thickness corresponding to the pixel is calculated, the first optical thickness calculated for each pixel, and the previously calculated absorption cross section of the target gas. Second optical based And calculating a slant column concentration of the target gas corresponding to the pixel, and generating information indicating a concentration distribution of the target gas based on the slant column concentration calculated for each pixel. An information processing method is provided.

In order to solve the above-described problem, according to another aspect of the present invention, different elevation angles may be used in an environment in which a computer is irradiated with light including a component of a band absorbed by a target gas to be observed. Acquiring the first image and the second image that are substantially the same in time taken, and for each corresponding pixel between the first image and the second image, the first image A first spectrum indicating the intensity of the component for each wavelength in the band in the pixel of the image and a second spectrum indicating the intensity of the component for the wavelength in the band of the pixel of the second image Based on the ratio, the first optical thickness corresponding to the pixel is calculated, the first optical thickness calculated for each pixel, and the previously calculated absorption cross section of the target gas. Second optics based Calculating the slant column concentration of the target gas corresponding to the pixel based on the thickness, and generating information indicating the concentration distribution of the target gas based on the slant column concentration calculated for each pixel. And a program for executing the above are provided.

  As described above, according to the present invention, an information processing apparatus, an information processing method, and a program capable of acquiring information indicating the spatial distribution of an air polluted gas or a warming gas are provided.

It is an explanatory view for explaining an example of a schematic system configuration of an observation system concerning an embodiment concerning one embodiment of the present invention. It is an example of the simulation result of the radiative transfer in the atmosphere. It is explanatory drawing for demonstrating the outline | summary of a spectral image. An example of a color image generated based on a spectral image captured in the direction of a low elevation angle is shown. An example of the spectrum in the pixel in the spectral image imaged about the direction of the low elevation angle is shown. An example of a color image generated based on a spectral image captured in the direction of a high elevation angle is shown. An example of a spectrum in a pixel in a spectral image captured in the direction of a high elevation angle is shown. It is the block diagram shown about an example of the function structure of the observation system which concerns on the same embodiment. It is the graph which showed an example of the relationship between the optical thickness calculated based on observation data, and a wavelength. It is the graph which showed an example of the relationship between the optical thickness from which the influence of Rayleigh scattering or Mie scattering was removed, and a wavelength. And the absorption cross section for each wavelength of NO _2, is a graph showing an example of a calculation result of the absorption cross-section for each wavelength of O _4. An example of a simulated transmittance spectrum is shown. An example of a simulated optical thickness spectrum calculated based on simulated transmittance is shown. An example of the result of fitting between an observed value and a simulation calculation value is shown. The other example of the result of the fitting between an observed value and a simulation calculation value is shown. It is an example of the color image information which shows the spatial distribution of object gas. It is explanatory drawing for demonstrating the outline | summary of the information processing apparatus 10 which concerns on the modification 1. FIG. It is the figure which showed an example of the observation result of a carbon dioxide. 10 is an explanatory diagram for explaining an example of a schematic system configuration of an observation system according to Modification 2. FIG. It is an example of the spectral image acquired sequentially along a time series about each direction of a low elevation angle and a high elevation angle. It is another example of the spectral image acquired sequentially along a time series about each direction of a low elevation angle and a high elevation angle. It is the figure which showed an example of the hardware constitutions of the information processing apparatus which concerns on the embodiment.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

<< 1. Overview of observation system >>
First, an overview of an observation system according to an embodiment of the present invention will be described. For example, FIG. 1 is an explanatory diagram for describing an example of a schematic system configuration of the observation system according to the present embodiment.

  As shown in FIG. 1, the observation system 1 according to the present embodiment includes an imaging device 20, a reflection unit 21, a storage unit 30, an information processing device 10, and a display device 50. Reference numeral 70 schematically shows a light source of illumination light that illuminates the observation environment.

The observation system 1 according to the present embodiment has an absorption spectrum in a predetermined band including ultraviolet, visible, and near infrared, and the magnitude of the absorption is observable by using a long optical path. Larger gas is the object of observation. More specifically, in the observation system 1 according to the present embodiment, when the fluctuation range of the optical thickness is Δτ, the observation target is a gas having a value of Δτ of 0.01 or more. . Examples of the gas having such characteristics include nitrogen dioxide (NO ₂ , so-called NOx), water vapor (H ₂ O), O ₂ , sulfur dioxide (SO ₂ , so-called SOx), ozone (O ₃ ), and carbon dioxide. (CO ₂ ), methane (CH ₄ ), and the like. These gases are different from each other in the absorption spectrum wavelength band and the absorption amount of the component of the wavelength.

For example, FIG. 2 is an example of a simulation result of radiative transfer in the atmosphere, and a simulation result of radiance for each wavelength for H ₂ O, NO ₂ , O ₂ (O ₄ ), and O _3. An example is shown. The simulation data shown in FIG. 2 is generated based on a computer code called MODTRAN5, which is disclosed by Spectral Sciences Inc. and AFRL (Air Force Research Laboratories), for simulating radiative transfer in the atmosphere. Yes.

In FIG. 2, it can be seen that the radiance in the wavelength band near 720 nm is lower than the surrounding wavelengths due to the absorption of H ₂ O. Further, the radiance in the wavelength band of 400 nm to 500 nm is lowered due to absorption of NO ₂ . In the observation system 1 according to the present embodiment, by using such characteristics (that is, the difference in the wavelength of the absorption spectrum and the difference in the absorption amount of the atmospheric component gas at the wavelength), the gas to be observed (hereinafter referred to as the target object) , Which is also referred to as “target gas”) (in other words, how the concentration distribution changes due to the difference in the viewing direction).

  From the characteristics as described above, in the observation system 1 according to the present embodiment, the environment is irradiated with light including at least components in the wavelength band of the absorption spectrum of the target gas (in other words, under illumination with light including the wavelength). Observations are made at. As a specific example, in the observation system 1 according to the present embodiment, sky light (scattered light of sunlight) may be used as illumination light. As described above, in the observation system 1, the spatial distribution of the target gas can be observed based on the absorption spectrum of the target gas. Therefore, when sky light (sunlight scattered light) is used as illumination light, for example, observation in an environment where the weather is uniformly sunny or cloudy is more desirable. This is because if there is a local cloud such as cumulus clouds, the spectrum will fluctuate rapidly, and the spectrum may change due to slight time differences, which may make stable analysis difficult. .

In the observation system 1 according to the present embodiment, the imaging device 20 can acquire data indicating the intensity of light for each wavelength in a predetermined band for one pixel of an image to be captured. A device capable of capturing a spectral image is applied. Further, the imaging device 20 is configured to be able to acquire at least data indicating the intensity of light for each wavelength in the band of the absorption spectrum of the gas to be observed (that is, the target gas). As a specific example, when NO ₂ is an observation target, as the imaging device 20, an apparatus capable of acquiring data indicating the intensity of light for each wavelength in a band of at least 400 nm to 500 nm is applied. Become. As the imaging device 20, for example, a hyperspectral camera manufactured by Eva Japan Co., Ltd. can be used. Of course, in the present embodiment, the configuration of the imaging device 20 is not particularly limited as long as a spectral image can be acquired.

  As shown in FIG. 1, in the observation system 1 according to the present embodiment, in an environment where sky light is irradiated, the imaging device 20 causes a low elevation angle direction (for example, an elevation angle of 30 degrees or less) and a high elevation angle. Spectral images are captured for each direction (for example, an elevation angle of 50 to 90 degrees), and each captured spectral image is an analysis target. Here, the spectroscopic image in the direction of the low elevation angle indicates, for example, a spectroscopic image based on the intensity of light reaching the imaging device 20 via the optical path indicated by the reference symbol L1 in FIG. Further, the spectral image in the direction of the high elevation angle indicates a spectral image based on the intensity of light reaching the imaging device 20 through the optical path indicated by reference symbol L2 in FIG. The direction of the low elevation angle corresponds to the direction of observing the spatial distribution of the gas to be observed (that is, the target gas).

  For example, in the example illustrated in FIG. 1, the optical path of light reaching the imaging device 20 is selectively switched between the optical paths L <b> 1 and L <b> 2 by the reflecting unit 21. The reflecting unit 21 is configured by, for example, an optical member such as a mirror, and switches an optical path of light reaching the imaging device 20 by reflecting or polarizing light. More specifically, in the example illustrated in FIG. 1, the reflection unit 21 switches the optical path of the light reaching the imaging device 20 between the optical paths L1 and L2 in a time division manner. A spectral image in the direction of low elevation angle and a spectral image in the direction of high elevation angle can be captured in a time-sharing manner.

  Note that, in the observation system 1 according to the present embodiment, the configuration is not necessarily limited to the example illustrated in FIG. 1 as long as spectral images in different elevation angle directions can be captured. For example, a plurality of imaging devices 20 may be provided, and spectral images in the direction of low elevation angle and spectral images in the direction of high elevation angle may be captured by different imaging devices 20, respectively. In addition, between the imaging devices 20 which are mutually different, the case where the shift | offset | difference arises between the spectral images imaged according to the characteristic can be assumed. Therefore, when a spectral image in the direction of low elevation angle and a spectral image in the direction of high elevation angle are imaged by different imaging devices 20, each spectral image to be captured is calibrated according to the characteristics of the imaging device 20. It is desirable. The calibration method will be described later separately.

  Here, an example of a spectral image captured by the imaging device 20 will be described. For example, FIG. 3 is an explanatory diagram for explaining an outline of a spectral image.

  As shown in FIG. 3, the spectral image D <b> 10 captured by the imaging device 20 includes an image D <b> 101 based on the intensity of the wavelength component for each wavelength in a predetermined band. Specifically, for example, the imaging device 20 separates incident light into a plurality of wavelength components using a spectroscopic element or the like, and responds to the intensity of each wavelength component based on the light reception result for each of the dispersed wavelengths. The generated image D101 is generated. Note that the number of images D101 for each wavelength included in the spectral image D10 and the resolution in the wavelength direction (λ-axis direction) are determined according to the characteristics of the imaging device 20 (for example, the performance of the imaging device and the number of channels). .

  From such a configuration, for example, by extracting and synthesizing an image D101 corresponding to a part of the wavelengths D101 for each wavelength included in the spectral image D10, an image based on the extracted wavelength component can be obtained. It is also possible to synthesize. As a specific example, a so-called color image (RGB image) can be synthesized by extracting an image D101 corresponding to each component of RGB and synthesizing the extracted image D101.

For example, the examples illustrated in FIGS. 4 to 7 illustrate examples of various data acquired from the spectral image captured by the imaging device 20. In addition, each spectral image corresponding to the example shown in FIGS. 4 to 7 is acquired for a band of 400 nm to 740 nm based on various conditions shown below with NO ₂ as an observation target.
Measurement device (imaging device 20): SIS-H manufactured by Eva Japan Co., Ltd.
・ Image size: 640 × 480
-Number of wavelength channels: 1024
・ Resolution in the wavelength direction: 0.3 nm
(However, the optical resolution determined by a light source with a narrow line width is 1.0 nm)
・ Observation date and time: February 16, 2015 11:40 JST
・ Line rate: 36 line per second

  Specifically, FIG. 4 shows an example of a color image generated based on a spectral image captured in the direction of a low elevation angle. In the example illustrated in FIG. 4, the spectral image is captured so that the building M11 that is 3.57 km away from the position where the imaging device 20 is installed is within the angle of view. In the example shown in FIG. 4, the horizontal direction is the x direction and the vertical direction is the y direction.

FIG. 5 shows an example of a spectrum at a pixel in a spectral image captured in the direction of a low elevation angle. Specifically, the example shown in FIG. 5 shows the spectrum of the pixel at the position (x, y) = (200, 200) indicated by the reference symbol P11 in the image shown in FIG. In FIG. 5, the horizontal axis indicates the wavelength (nm), and the vertical axis indicates the count value of the signal detected by each pixel (that is, the magnitude of the radiance at the corresponding wavelength). In the example shown in FIG. 5, it can be seen that the count value of the wavelength decreases for some wavelengths. This is presumed that the component of the corresponding wavelength was absorbed by NO ₂ , H ₂ O, O ₂ , O _{4 and the} like.

  FIG. 6 shows an example of a color image generated based on a spectral image captured in the direction of a high elevation angle. In the example illustrated in FIG. 6, the spectral image is captured at an elevation angle of 57 degrees at the position where the spectral image corresponding to the example illustrated in FIG. 4 is captured. In the example shown in FIG. 6, the horizontal direction is the x direction and the vertical direction is the y direction, as in the example shown in FIG. Further, in FIG. 6, the pixel indicated by the reference symbol P21 corresponds to the pixel indicated by the reference symbol P11 in FIG. That is, the pixel P21 indicates the pixel at the position (x, y) = (200, 200).

  FIG. 7 shows an example of a spectrum in a pixel in a spectral image captured in the direction of a high elevation angle. Specifically, the example shown in FIG. 7 shows the spectrum at the pixel P21 in the image shown in FIG. In addition, the vertical axis | shaft and horizontal axis | shaft in FIG. 7 are the same as that of the example shown in FIG.

  Here, with reference to FIG. 1 again, another configuration of the observation system 1 according to the present embodiment will be described.

  The storage unit 30 is a storage area for storing data used for various types of analysis for the information processing apparatus 10 to be described later to generate information indicating the distribution (concentration distribution) of the target gas. For example, the imaging device 20 may cause the storage unit 30 to store spectral images captured in the directions of the low elevation angle and the high elevation angle.

  The display device 50 is an output device configured to output image information such as a still image or a moving image, such as a so-called display.

  The information processing apparatus 10 executes various analysis processes based on a spectral image captured by the imaging apparatus 20 (that is, a spectral image captured in each of the low elevation angle and high elevation angle directions), thereby performing spectral analysis in the direction of the low elevation angle. Information indicating the spatial distribution of the target gas in the line-of-sight direction of the region corresponding to the image (that is, the region contained within the angle of view in the low elevation angle direction) is generated. Note that details of various analysis processes related to generation of information indicating the spatial distribution of the target gas by the information processing apparatus 10 will be described later.

  Note that the information processing apparatus 10 may cause the storage unit 30 to store information indicating the spatial distribution of the generated target gas. Further, the information processing apparatus 10 may generate image information that presents information indicating the spatial distribution of the target gas so as to be identifiable, and cause the display apparatus 50 to output the image information.

  The overview of the observation system according to the embodiment of the present invention has been described above with reference to FIGS.

<< 2. Functional configuration >>
Next, an example of a functional configuration of the observation system 1 according to the present embodiment will be described, particularly focusing on processing related to generation of information indicating the spatial distribution of the target gas by the information processing apparatus 10. For example, FIG. 8 is a block diagram illustrating an example of a functional configuration of the observation system 1 according to the present embodiment. Note that the information processing device 10, the imaging device 20, the storage unit 30, and the display device 50 illustrated in FIG. 8 are the same as the information processing device 10, the imaging device 20, the storage unit 30, and the display device 50 illustrated in FIG. It corresponds. Therefore, in this description, the description will be given with particular attention to an example of data stored in the storage unit 30 and a more detailed configuration of the information processing apparatus 10.

(Storage unit 30)
As shown in FIG. 8, examples of data stored in the storage unit 30 include observation data 31, calibration data 33, simulation data 35, and output data 37.

  The observation data 31 indicates data acquired as an observation result, and includes, for example, a spectral image in the low elevation angle direction and a spectral image in the high elevation direction imaged by the imaging device 20.

  The calibration data 33 is data for calibrating the pixel value (that is, light intensity) in each pixel of the spectral image captured by the imaging device 20. Examples of the calibration data 33 include wavelength calibration data and field angle calibration data.

  The wavelength calibration data is calibration data for correcting a spectral shift that occurs between pixels. Specifically, the wavelength recorded by a specific pixel is shifted by a slight shift in the optical path from the slit of the spectroscope through the diffraction grating to the detector. The wavelength calibration data is data in which a correction coefficient for correcting a spectral shift generated between the pixels is recorded for each pixel. As for wavelength calibration data, for example, a mercury lamp that emits a sharp emission line spectrum, a laser beam having a well-known wavelength (for example, an Nd: YAG laser, a He—Ne laser), or the like is used for observation. It may be generated in advance based on the amount of spectral shift for each pixel obtained by imaging. In addition, there may be a difference in count value between pixels due to variations in sensitivity among pixels. In order to calibrate the sensitivity, an object such as a screen that can be regarded as having uniform brightness is prepared, and this is imaged to examine the difference in count value for each pixel.

  The angle of view calibration data is data for calibrating the deviation (distortion) of the angle of view caused by the optical characteristics of the imaging optical system. The angle-of-view calibration data may be generated in advance according to the optical characteristics of an imaging optical system such as a lens used for imaging a spectral image, for example. Note that the method of generating the angle-of-view calibration data is generally known and will not be described in detail.

  The simulation data 35 is data indicating characteristics for each wavelength of the target gas, which is calculated by using known information as an absorption cross-sectional area for each wavelength of the target gas. Note that the information processing apparatus 10 described later generates information indicating the spatial distribution of the target gas based on the acquired observation data 31 and the calculated simulation data 35. Note that details of the simulation data 35 and details of the calculation method of the simulation data 35 will be described later.

  The output data 37 corresponds to data generated by the information processing apparatus 10 described later. Examples of the output data 37 include information indicating the spatial distribution of the target gas generated based on the observation data 31 and the simulation data 35. In addition, information (for example, image information) for presenting the spatial distribution of the target gas so as to be identifiable to the user may be stored as the output data 37.

(Information processing apparatus 10)
The information processing apparatus 10 includes an analysis unit 11 and an output control unit 13.

The analysis unit 11 is configured to generate information indicating the spatial distribution of the target gas based on the observation data 31 and the simulation data 35. Hereinafter, an example of more detailed operation of the analysis unit 11 will be described by taking, as an example, a case where NO ₂ is the target gas (that is, a case where information indicating the spatial distribution of NO ₂ is generated).

First, the analysis unit 11 reads the spectral images in the directions of the low elevation angle and the high elevation angle stored as the observation data 31 in the storage unit 30, and for each corresponding pixel between the read spectral images, between the spectral images. Calculate the spectral ratio. For example, let I (λ) be the spectrum at each pixel of the spectral image corresponding to the direction of the low elevation angle (that is, the function representing the wavelength dependence of the radiance value), and each pixel of the spectral image corresponding to the direction of the high elevation angle. Let the spectrum be I ₀ (λ). In this case, the analysis unit 11 calculates I (λ) / I ₀ (λ) for each corresponding pixel between the spectral images in the directions of the low and high elevation angles. In this way, by calculating the ratio between the spectral images in the low and high elevation directions, the information in the sky, which is normally considered to be less dependent on the direction, is deleted, and the low elevation angle, that is, depending on the direction near the ground. The slant column concentration (details will be described later) can be extracted quantitatively.

The spectrum shown in FIG. 5 corresponds to an example of the spectrum I (λ) for each pixel in the spectral image corresponding to the direction of the low elevation angle. The spectrum shown in FIG. 7 corresponds to an example of the spectrum I ₀ (λ) for each pixel in the spectral image corresponding to the direction of the high elevation angle. In the following description, I (λ) is also simply referred to as “corresponding spectrum corresponding to a low elevation angle”. Similarly, I ₀ (λ) is also simply referred to as “corresponding spectrum corresponding to high elevation angle”.

Next, the analysis unit 11 performs wavelength calibration and angle of view calibration on the spectrum I (λ) for each pixel in the spectral image corresponding to the direction of the low elevation angle based on the calibration data 33 stored in the storage unit 30. Perform calibration processing. Then, based on the calculation result of I (λ) / I ₀ (λ) for each pixel based on I (λ) subjected to the calibration process, the analysis unit 11 performs a moving average of a 5 × 5 region for each pixel. Is calculated. In the following processing, it is assumed that the calculated moving average indicates the value of I (λ) / I ₀ (λ) in the corresponding pixel.

Next, the analysis unit 11 uses I (λ) / I ₀ (λ) calculated for each pixel as an input, and corresponds to the pixel based on Lambert-Beer's law shown as (Equation 1) below. The optical thickness τ (λ) is calculated.

  For example, the following (Formula 2) shows an example of a formula for calculating the optical thickness τ (λ) for each pixel based on the Lambert-Beer law shown as (Formula 1). In (Equation 2), log means a natural logarithm.

Here, based on the spectrum corresponding to the low elevation angle shown in FIG. 5 and the spectrum corresponding to the high elevation angle shown in FIG. 7, the optical thickness calculated based on (Equation 2) shown above is calculated. _Assuming that τ _obs (λ), the relationship between the wavelength λ and the optical thickness τ _obs (λ) is represented by the graph shown in FIG. FIG. 9 is a graph showing an example of the relationship between the optical thickness τ _obs (λ) calculated based on the observation data and the wavelength λ. In FIG. 9, the horizontal axis indicates the wavelength λ (nm), and the vertical axis indicates the optical thickness.

Next, the analysis unit 11 expresses a component that gradually changes with respect to the wavelength by using a third-order polynomial p (λ), and calculates the optical thickness τ (λ calculated based on I (λ) / I ₀ (λ). ) Is subtracted from p (λ). As a result, effects such as Rayleigh scattering (scattering by atmospheric molecules such as nitrogen and oxygen) and Mie scattering (scattering by aerosol) are removed from the optical thickness τ (λ). Here, when the result obtained by subtracting the polynomial p (λ) from the optical thickness τ _obs (λ) is τ ′ _obs (λ), the optical thickness τ ′ _obs (λ) is as follows: Is expressed by a calculation formula shown as (Formula 3).

Further, the relationship between the wavelength λ and the optical thickness τ ′ _obs (λ) is represented by the graph shown in FIG. FIG. 10 is a graph showing an example of the relationship between the optical thickness τ ′ _obs (λ) from which the influence of Rayleigh scattering and Mie scattering has been removed, and the wavelength λ. In FIG. 10, the horizontal axis indicates the wavelength λ (nm), and the vertical axis indicates the optical thickness.

  The process shown as (Equation 3) corresponds to a process of subtracting a so-called “DC-like” component that gradually changes with respect to the wavelength, and even when “low frequency removal” is performed using Fourier transform. Similar results are obtained. Note that increasing the degree of the polynomial corresponds to removing even higher frequency components.

Next, the analysis unit 11 generates simulation data 35. Specifically, the analysis unit 11 first determines the absorption cross section for each wavelength of the gas to be analyzed including the gas to be observed (that is, the target gas) according to the temperature at the time of observation. Calculate based on information. In the following description, the absorption cross section of the gas g at the wavelength λ may be expressed as σ _g (λ). Here, since the absorption of molecules other than NO ₂ and O ₄ is small in the wavelength band of 400 to 500 nm, the analysis unit 11 calculates the absorption cross section σ _g (λ) for each wavelength for NO ₂ and O _4. . The absorption cross section σ _g (λ) for each wavelength of NO ₂ and O ₄ according to the temperature at the time of observation is, for example, HITRAN (an acronym for High Resolution) published on the Harvard Smithsonian Center website. It can be calculated by using the (Transmission) database. Note that the wavelength resolution in calculating the absorption cross section σ _g (λ) for each wavelength of the gas to be analyzed (for example, NO ₂ and O ₄ ) is sufficiently larger than the wavelength resolution of the absorption line of each gas. Make it fine.

For example, FIG. 11 is a graph showing an example of the calculation results of the absorption cross section σ _NO2 (λ) for each wavelength of NO ₂ and the absorption cross section σ _O4 (λ) for each wavelength of O ₄ . In FIG. 11, the horizontal axis indicates the wavelength λ (nm), and the vertical axis indicates the absorption cross section for each wavelength of NO ₂ and O ₄ .

Note that when the gas whose absorption cross-sectional area is not relatively temperature dependent is to be analyzed, the temperature set as the calculation condition for the absorption cross-section σ _g (λ) does not necessarily match the temperature at the time of observation. It does not have to be. As a specific example, in a normal environment, the temperature dependence of the absorption cross section of both NO ₂ and O ₄ is not relatively large. Therefore, for example, for NO ₂ , even if an absorption cross section corresponding to 294K is used, and for O ₄ , an absorption cross section of 296K is used, it can be considered that the error is not large.

Next, the analysis unit 11 performs differential slant column concentration ΔSCD _g (g = NO ₂ , O ₄ ) and transmittance T _g (ΔSCD _g , λ) for the gas to be analyzed (ie, NO ₂ and O ₄ ). ) Is generated.

Specifically, the analysis unit 11 sets the differential slant column concentration ΔSCD _g to, for example, 10 ⁻² , 10 ^−1.9 ,..., 10 ^1.9 , 10 with respect to an appropriate initial value (a priori value). Calculated by multiplying by ² . Further, the analysis unit 11 calculates the corresponding transmittance T _g (ΔSCD _g , λ) for each ΔSCD _g based on the calculation formula shown below as (Equation 4).

Next, the analysis unit 11 adjusts the wavelength resolution of the transmittance T _g (ΔSCD _g , λ) calculated for each ΔSCD _g according to the wavelength resolution of the imaging device 20 from which the observation data 31 is acquired. When the transmittance after adjustment of the wavelength resolution is T _g ′ (ΔSCD _g , λ), the transmittance T _g ′ (ΔSCD _g , λ) is calculated as (Equation 5) below. Calculated based on the formula.

  In (Expression 5) shown above, the coefficient μ is a value determined according to the performance of the imaging device 20. As a specific example, when the wavelength resolution of the imaging device 20 is 1.0 nm, μ = 1.0.

Next, the analysis unit 11 calculates a simulated transmittance spectrum based on the generated lookup table. Specifically, the analysis unit 11 assumes the value of the differential slant column concentration ΔSCD _g (g = NO ₂ , O ₄ ), and uses the look-up table and spline interpolation to transmit the transmittance T _g ′ (ΔSCD _g , Λ). And the analysis part 11 calculates simulated transmittance _| permeability _Tsim ((lambda)) based on the calculation formula shown as (Formula 6) below.

  For example, FIG. 12 shows an example of a simulated transmittance spectrum. In FIG. 12, the horizontal axis indicates the wavelength (nm) and the vertical axis indicates the transmittance.

Next, the analysis unit 11 calculates the simulated optical thickness τ _sim (λ) by taking the logarithm of the calculated simulated transmittance T _sim (λ) and inverting the sign. That is, the simulated optical thickness τ _sim (λ) is calculated based on a calculation formula shown as (Formula 7) below.

Further, analyzer 11 calculates from the calculated simulated optical thickness τ _{sim (λ),} by subtracting the component q (lambda) that vary slowly with respect to the wavelength, the simulated optical thickness tau _'sim a _(lambda) To do. That is, the simulated optical thickness τ ′ _sim (λ) is calculated based on the calculation formula shown as (Formula 8) below.

Note that the simulated optical thickness τ _sim (λ) itself does not include the influence of scattering of air molecules and aerosols. However, in the optical thickness τ ′ _obs (λ) calculated based on the above (Equation 3), a direct current component included in the absorption of NO ₂ or O ₄ itself is subtracted, so that the simulated optical Similarly, for the thickness τ _sim (λ), the simulated optical thickness τ ′ _sim (λ) is calculated by subtracting the DC component q (λ).

For example, FIG. 13 shows an example of a spectrum of simulated optical thickness calculated based on simulated transmittance. In FIG. 13, the horizontal axis indicates the wavelength (nm) and the vertical axis indicates the optical thickness. In the example shown in FIG. 13, a graph is shown for each of the simulated optical thickness τ _sim (λ) and the simulated optical thickness τ ′ _sim (λ) from which a direct current component has been subtracted.

Next, the analysis unit 11 calculates based on the optical thickness τ ′ _obs (λ) (hereinafter also referred to as “observed value”) calculated based on the above-described (Formula 3) and based on the above-described (Formula 6). The simulated optical thickness τ ′ _sim (λ) (hereinafter also referred to as “simulated calculation value”) is compared. At this time, when there is a difference between the observed value τ ′ _obs (λ) and the simulated calculated value τ ′ _sim (λ) (for example, when the amount of slip exceeds the threshold value), the analysis unit 11 determines the difference slant column concentration. The simulated calculation value τ ′ _sim (λ) is recalculated by changing the assumed value of ΔSCD _g (g = NO ₂ , O ₄ ). Thus, the analysis unit 11, by repeating 'the calculation of the _{sim (lambda),} the calculated simulated Calculated tau' simulated Calculated tau and compared with the _{sim (lambda)} and the observed value τ _{'obs (λ)} Then, the simulation calculation value τ ′ _sim (λ) that substantially matches the observation value τ ′ _obs (λ) is searched and specified. The simulated calculation value τ ′ _sim (λ) corresponds to an example of the simulation data 35 described above. In addition, a lookup table that associates the above-described differential slant column concentration ΔSCD _g (g = NO ₂ , O ₄ ) with the transmittance T _g (ΔSCD _g , λ) may be stored as the simulation data 35.

Then, the analysis unit 11 uses the assumed value of the differential slant column concentration ΔSCD _g (g = NO ₂ , O ₄ ), which is the calculation source of the specified simulated calculation value τ ′ _sim (λ), as the differential slant column in the corresponding pixel. It is specified as the optimum value of the concentration ΔSCD _g (g = NO ₂ , O ₄ ). As a specific example, in the analysis corresponding to the pixel P11 in the image shown in FIG. 4, the difference slant column concentration ΔSCD _g (g = NO ₂ ) = 2.6 × 10 ¹⁷ molec / cm ² , the difference slant column The concentration ΔSCD _g (g = O ₄ ) = 8.4 × 10 ⁴³ molec ² / cm ⁵ was obtained.

For example, FIG. 14 shows an example of a fitting result between the observed value τ ′ _obs (λ) and the simulated calculated value τ ′ _sim (λ) (in other words, the simulated value). Specifically, the example illustrated in FIG. 14 includes the observation value τ ′ _obs (λ) based on the analysis result of the spectral image captured by the imaging device 20 as illustrated in FIG. 10 and the simulation illustrated in FIG. An example of a fitting result between the calculated value τ ′ _sim (λ) (in other words, a simulation value) is shown. Note that the horizontal and vertical axes in FIG. 14 are the same as those in FIGS. 10 and 13. Further, the example shown in FIG. 14 shows an example of fitting in the case where the contributions of both NO ₂ and O ₄ are considered. In the example shown in FIG. 14, the graph shown as “Data” corresponds to the observed value τ ′ _obs (λ), and the graph shown as “Simulation” corresponds to the simulated calculation value τ ′ _sim (λ). Yes.

FIG. 15 shows another example of the result of fitting between the observed value τ ′ _obs (λ) and the simulated calculated value τ ′ _sim (λ). Note that the example shown in FIG. 15 shows an example of fitting when only the contribution of NO ₂ is considered without considering the contribution of O ₄ . Further, in the example shown in FIG. 15, the vertical axis and the horizontal axis, the correspondence between the observed value τ ′ _obs (λ), the simulated calculated value τ ′ _sim (λ), and each graph are shown in FIG. 14. Similar to the example.

In the fitting in the wavelength band of 460 to 490 nm, the contribution of O ₄ is smaller than the contribution of NO ₂ . However, as can be seen from a comparison between FIG. 14 and FIG. 15, if the contribution of O ₄ is ignored, the difference between the observed value τ ′ _obs (λ) and the simulated calculated value τ ′ _sim (λ) growing. This indicates that it is more desirable to consider the contribution of O ₄ when analyzing NO _{2 in} the 460 to 490 nm band.

On the other hand, if the direct emission sources of NO ₂ is present, the value of the difference slant column density ΔSCD _{g (g} = NO ₂₎ is a value having a correlation with the emissions of NO _2. Therefore, in the observation targeting a position relatively close to the emission source, it is expected that the effect when considering the contribution of O ₄ is lower than that in the above-described example. Given the above, (in other words, for a typical air pollution) emissions sources NO ₂ may not exist in the angle of view, the value of ΔSCD _{g (g} = NO ₂₎ is air pollution caused by NO ₂ There is a direct correlation with the degree of. On the other hand, the value of ΔSCD _g (g = O ₄ ) indicates that oxygen molecules (O ₂ ) in the atmosphere are almost uniformly distributed, and a certain proportion of them is oxygen dimer (O ₄ ). In other words, the amount of light in the line-of-sight direction correlates with the effective optical path length that has passed through the atmosphere.

The analysis unit 11 performs the series of processes described above on each pixel of a spectral image (for example, a spectral image in the direction of a low elevation angle) that is a target for observing the spatial distribution of the target gas. The differential slant column concentration ΔSCD _g (g = NO ₂ ) in each pixel is calculated. Note that the analysis unit 11 may store information indicating the difference slant column concentration ΔSCD _g (g = NO ₂ ) calculated for each pixel in the storage unit 30 as the output data 37. Further, the analysis unit 11 may output information indicating the difference slant column concentration ΔSCD _g (g = NO ₂ ) calculated for each pixel to the output control unit 13 described later. Note that the information indicating the differential slant column concentration ΔSCD _g (g = NO ₂ ) calculated for each pixel corresponds to an example of information indicating the spatial distribution of the target gas (in this case, NO ₂ ).

  The output control unit 13 generates output information in which the spatial distribution of the target gas is presented in an identifiable manner based on the analysis result of the analysis unit 11, and outputs the output information to the user via an output device such as the display device 50. Present.

As a specific example, the output control unit 13 reads information indicating the difference slant column concentration ΔSCD _g (g = NO ₂ ) calculated for each pixel from the storage unit 30. As another example, the output control unit 13 may directly acquire information indicating the difference slant column concentration ΔSCD _g (g = NO ₂ ) calculated for each pixel from the analysis unit 11. Next, the output control unit 13 determines, for each pixel, the pixel value (“pixel value”) of the pixel according to the value of information indicating the difference slant column concentration ΔSCD _g (g = NO ₂ ) calculated for each pixel corresponding to the pixel. For example, RGB values are assigned. Through such processing, the output control unit 13 generates image information indicating the spatial distribution of the target gas. For example, FIG. 16 is an example of image information indicating the spatial distribution of the target gas. The example shown in FIG. 16 analyzes the spectral image in the direction of low elevation corresponding to the example shown in FIGS. 4 and 5 and the spectral image in the direction of high elevation corresponding to the example shown in FIGS. An example is shown.

  Then, the output control unit 13 displays the generated image information on the display device 50, thereby presenting the image information to the user via the display device 50. Thereby, for example, the user can recognize the spatial distribution of the target gas (in other words, the concentration distribution of the target gas) based on the color information in the presented image. Further, the output control unit 13 may store the generated image information as output data 37 in the storage unit 30.

  Note that the series of processes described above as functions of the information processing apparatus 10 is merely an example, and is not necessarily limited to the processes described above. For example, additional processes may be added. As a specific example, in the example shown in FIG. 4, the distance from the imaging device 20 to the building M11 can be calculated separately. Therefore, for example, the calculated value of the optical thickness depending on the optical path length (that is, the distance) may be corrected based on the distance information acquired by another method. Further, the series of processing flow described above corresponds to an example of an information processing method related to generation of information indicating the spatial distribution of the target gas.

  As described above, with reference to FIGS. 8 to 16, with regard to an example of the functional configuration of the observation system 1 according to the present embodiment, particularly, attention is focused on processing related to generation of information indicating the spatial distribution of the target gas by the information processing apparatus 10. Explained.

<< 3. Modification >>
Next, a modification of this embodiment will be described.

<3.1. Modification Example 1: Example of Using CO ₂ as Target Gas>
First, as a first modification, an example in which carbon dioxide (CO ₂ ) is used as a target gas will be described as an example in which a gas other than NO _{2 is used} as the target gas. For example, FIG. 17 is an explanatory diagram for explaining an overview of the information processing apparatus 10 according to the first modification, and shows an example of the wavelength characteristic of the CO ₂ absorption cross section. In FIG. 17, the horizontal axis indicates the wavelength (nm), and the vertical axis indicates the absorption cross-sectional area (au). In addition, in FIG. 17, in addition to the frequency characteristic of the absorption cross section of CO ₂ , the frequency characteristic of the absorption cross section of water vapor (H ₂ O) and HDO that is an isotope of H ₂ O is also combined as a reference. Presents.

As shown in FIG. 17, it can be seen that CO ₂ has a higher absorption cross-section value (in other words, has an absorption spectrum) in the band of 1565 nm to 1585 nm. Therefore, in the observation system 1 according to the embodiment described above, the imaging apparatus 20, for example, by applying the possible acquisition device data indicating the intensity of light for each wavelength in the band of 1550Nm～1600nm, the CO ₂ It is possible to observe the spatial distribution. Particularly, in the infrared absorption (vibrational rotation transition) of CO ₂ , as shown in FIG. 17, it is possible to separate and observe individual absorption lines having different rotational states.

For example, FIG. 18 is a diagram illustrating an example of the observation result of carbon dioxide (CO ₂ ). When CO ₂ is the target gas, the spectrum of the pixel in the spectral image captured in the direction of the low elevation angle is illustrated. An example is shown. In FIG. 18, the horizontal axis indicates the wavelength (nm), and the vertical axis indicates the count value of the signal detected by each pixel (that is, the intensity of the corresponding component). Incidentally, in the case where the CO ₂ and the target gas, the method of calculating the information indicating the spatial distribution of the CO _2, a detailed description for the same case of the target gas to NO ₂ as described above will be omitted.

As described above, with reference to FIGS. 17 and 18, as a first modification, an example in which carbon dioxide (CO ₂ ) is the target gas will be described as an example in which a gas other than NO ₂ is the target gas. did.

As described above, water vapor (H ₂ O), O ₂ , sulfur dioxide (SO ₂ , so-called SOx), ozone (O ₃ ), methane (CH ₄ ), and the like can be used as the target gas. As a more specific example, when water vapor (H ₂ O) is the target gas, an absorption band with a wavelength of 720 nm may be used. Further, when O ₂ is the target gas, an absorption band with a wavelength of 760 nm may be used. Further, when the target gas sulfur dioxide (SO _2), it is sufficient to use an absorption band at a wavelength 290Nm～320nm. Further, when ozone (O ₃ ) is used as a target gas, an absorption band having a wavelength of 280 nm to 320 nm may be used. Further, in the case of methane (CH ₄₎ and the target gas may be utilized absorption band wavelength 1620Nm～1720nm. Note that a band for acquiring data indicating the intensity of light for each wavelength is determined according to the absorption spectrum corresponding to the gas selected as the target gas, and the data of the band is used as the imaging device 20 (strictly, an image sensor). A device capable of obtaining the above may be applied.

<3.2. Variation 2: Observation of changes in the spatial distribution of the target gas in time series>
Next, as a second modification, an example of a method for observing a change along the time series of the spatial distribution of the target gas will be described.

  For example, FIG. 19 is an explanatory diagram for explaining an example of a schematic system configuration of an observation system 1 ′ according to the second modification. The observation system 1 ′ shown in FIG. 19 is different from the observation system 1 shown in FIG. 1 in that the spectral images in the directions of the low elevation angle and the high elevation angle are individually taken by different imaging devices 20 a and 20 b. Specifically, in the example illustrated in FIG. 19, the imaging device 20a captures a spectral image based on the intensity of light reaching via the optical path L1. In addition, the imaging device 20b captures a spectral image based on the intensity of light reaching via the optical path L2. In the following description, the imaging devices 20a and 20b may be simply referred to as “imaging device 20” unless they are particularly distinguished.

  In the observation system 1 ′ according to the second modification, each of the imaging devices 20 a and 20 b sequentially captures a spectral image along a time series at a predetermined frame rate. As a result, a moving image using each spectral image as a frame is captured in each of the low and high elevation directions. For example, FIG. 20 shows an example of a spectral image sequentially acquired along the time series in the directions of the low elevation angle and the high elevation angle based on the observation system 1 ′ shown in FIG. 19. In FIG. 20, reference numerals D11 to D15 indicate examples of spectral images sequentially acquired along the time series in the direction of the low elevation angle. Reference numerals D21 to D25 indicate examples of spectral images sequentially acquired along the time series in the direction of the high elevation angle.

In the example shown in FIG. 20, the spectral image D11 of low elevation angle, each of the high elevation angle direction of the spectral image D21, it shows the spectral image captured time t _1. Similarly, the low elevation angle direction of the spectral image D12～D15, each of the high elevation angle direction of the spectral image D22～D25, shows the spectral image captured time _t 2 ~t _5.

In the observation system 1 ′ according to the modification 2, for example, the information processing apparatus 10 regards the spectral images in the directions of the low elevation angle and the high elevation angle at which the captured times substantially coincide with each other as the spectral images of the same frame. As a specific example, in the example shown in FIG. 20, the information processing apparatus 10, captured in time t _1, the direction of the spectral image D11 of a low elevation angle, and a high elevation angle direction of the spectral image D21, the same frame May be regarded as a spectral image. Similarly, the information processing apparatus 10, captured in time t _3, the direction of the spectral image D13 of a low elevation angle, and a high elevation angle direction of the spectral image D23, may be regarded as the spectral image of the same frame.

  Then, the information processing apparatus 10 regards the spectral images in the directions of the low elevation angle and the high elevation angle, which are regarded as the spectral images of the same frame, as the object of analysis, and based on the same method as in the above-described embodiment, Information indicating the general distribution is calculated. At this time, it is more desirable that the information processing apparatus 10 calibrate each spectral image based on calibration data corresponding to the characteristics of the imaging apparatus 20 that is the imaging source.

As described above, the information processing apparatus 10 calculates the information indicating the spatial distribution of the target gas for each frame along the time series. For example, in the case of the example illustrated in FIG. 20, information indicating the spatial distribution of the target gas is calculated for each of the times t _{1 to} t ₅ . Based on such a configuration, for example, by generating image information as shown in FIG. 16 for each piece of information indicating the spatial distribution of the target gas calculated for each frame, the time series of the spatial distribution of the target gas It is also possible to visualize the change along the video as a moving image.

In the example shown in FIG. 19, a one-dimensional measurement portable spectrometer may be applied to the direction of the high elevation angle instead of the imaging device 20 b that can capture a two-dimensional image. Examples of such a portable spectrometer include MS-720 manufactured by Eihiro Seiki Co., Ltd. In this case, the ratio of the spectrum I (λ) in each pixel of the spectral image captured by the imaging device 20a to the spectrum I ₀ (λ) acquired as a measurement result of the one-dimensional measurement portable spectrometer. Based on this, the optical thickness τ _obs (λ) at the pixel may be calculated.

  In the example described with reference to FIGS. 19 and 20, the spectral images in the directions of the low elevation angle and the high elevation angle are taken by different imaging devices 20a and 20b, but are not necessarily limited to the same configuration. Not. As a specific example, as shown in FIG. 1, a single imaging device 20 may capture time-division spectral images in the low and high elevation directions.

For example, FIG. 21 shows time-division imaging of spectral images in the low elevation angle and high elevation angle directions as another example of the spectral images sequentially acquired along the time series in the low elevation angle and high elevation angle directions. An example of the case is shown. In the example illustrated in FIG. 21, the imaging device 20 captures the spectral images D11, D13, and D15 in the low elevation direction at times t ₁ , t ₃ , and t ₅ , and at times t ₂ and t ₄ , Spectral images D22 and D24 in the direction of low elevation angle are taken.

In this case, the information processing apparatus 10 converts the spectral image in the low elevation angle direction and the spectral image in the high elevation angle direction, in which the captured times are located near each other on the time axis, to the spectral image of the same frame. In view of this, information indicating the spatial distribution of the target gas corresponding to the frame may be calculated. As a specific example, in the example shown in FIG. 21, the information processing apparatus 10 includes a spectral image D11 in the direction of a low elevation angle corresponding to the time t _1, the spectral image D22 in the direction of the high elevation angle corresponding to the time t ₂ May be regarded as spectral images of the same frame.

  In this case, there is a shift in imaging time between the spectral image in the direction of low elevation angle and the spectral image in the direction of high elevation angle, and the spatial distribution of the target gas calculated due to the shift in imaging time There may be an error in the information indicating. However, when the amount of change in the spatial distribution of the target gas within the angle of view where the spectral image is captured is small at the spectral image capturing interval (in other words, the spatial distribution of the target gas changes within the angle of view). When the spectral image capturing interval is sufficiently fast relative to the speed), the error can be ignored.

As another example, the information processing apparatus 10 may interpolate other spectral images based on a plurality of captured spectral images. For example, in the example shown in FIG. 21, which spectral image D12 in the direction of a low elevation angle corresponding to the time t ₂ is not captured. At this time the information processing apparatus 10, for example, by interpolation processing based on the spectral image D11 and D13 in the direction of a low elevation angle corresponding to the time t ₁ and t ₃ when adjacent time t ₂ on the time axis, to the time t ₂ A spectral image 12 in the direction of the corresponding low elevation angle may be generated. The same applies to the spectral image D14 in the low elevation angle direction and the spectral images D21, D23, and D25 in the high elevation angle direction. By such processing, as in the example described with reference to FIGS. 19 and 20, it is also possible to calculate information indicating the spatial distribution of the target gas corresponding to each of the times t _{1 to} t _5. is there.

  As described above, as a second modification, an example of a method for observing a change along the time series of the spatial distribution of the target gas will be described with reference to FIGS. 19 to 21.

<< 4. Hardware configuration >>
Next, an example of a hardware configuration of the information processing apparatus 10 according to an embodiment of the present disclosure will be described with reference to FIG. FIG. 22 is a diagram illustrating an example of a hardware configuration of the information processing apparatus 10 according to an embodiment of the present disclosure.

  As illustrated in FIG. 22, the information processing apparatus 10 according to the present embodiment includes a processor 901, a memory 903, a storage 905, an operation device 907, a notification device 909, an imaging device 913, and a bus 917. . Further, the information processing apparatus 10 may include a communication device 911.

  The processor 901 may be, for example, a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), a DSP (Digital Signal Processor), or a SoC (System on Chip), and executes various processes of the information processing apparatus 10. The processor 901 can be configured by, for example, an electronic circuit for executing various arithmetic processes. The analysis unit 11 and the output control unit 13 described above can be realized by the processor 901.

  The memory 903 includes a RAM (Random Access Memory) and a ROM (Read Only Memory), and stores programs and data executed by the processor 901. The storage 905 can include a storage medium such as a semiconductor memory or a hard disk. For example, the storage unit 30 described above can be realized by at least one of the memory 903 and the storage 905, or a combination of both.

  The operation device 907 has a function of generating an input signal for a user to perform a desired operation. The operation device 907 can be configured as a touch panel, for example. As another example, the operation device 907 generates an input signal based on an input by the user, such as buttons, switches, and a keyboard, and an input for the user to input information, and supplies the input signal to the processor 901. It may be composed of a control circuit or the like.

  The notification device 909 is an example of an output device, and may be a device such as a liquid crystal display (LCD) device or an organic light emitting diode (OLED) display, for example. In this case, the notification device 909 can notify the user of predetermined information by displaying the screen. For example, the display device 50 described above can be realized by the notification device 909.

  Further, the notification device 909 may be a device that notifies a user of predetermined information by outputting a predetermined acoustic signal, such as a speaker.

  Note that the example of the notification device 909 described above is merely an example, and the manner of the notification device 909 is not particularly limited as long as predetermined information can be notified to the user. As a specific example, the notification device 909 may be a device that notifies the user of predetermined information by a lighting or blinking pattern, such as an LED (Light Emitting Diode).

  The communication device 911 is a communication unit included in the information processing apparatus 10 and communicates with an external device via a network. The communication device 911 is a wired or wireless communication interface. When the communication device 911 is configured as a wireless communication interface, the communication device 911 may include a communication antenna, an RF (Radio Frequency) circuit, a baseband processor, and the like.

  The communication device 911 has a function of performing various kinds of signal processing on a signal received from an external device, and can supply a digital signal generated from the received analog signal to the processor 901.

  The imaging device 913 includes an imaging element that captures a subject and obtains digital data of the captured image, such as a complementary metal-oxide semiconductor (CMOS) image sensor or a charge coupled device (CCD) image sensor. That is, the imaging device 913 has a function of capturing a still image or a moving image via an optical system such as a lens in accordance with the control of the processor 901. The imaging device 913 may store the captured image in the memory 903 or the storage 905. For example, the above-described imaging device 20 can be realized by the imaging device 913.

  The bus 917 connects the processor 901, the memory 903, the storage 905, the operation device 907, the notification device 909, the communication device 911, and the imaging device 913 to each other. The bus 917 may include a plurality of types of buses.

  In addition, it is possible to create a program for causing hardware such as a processor, a memory, and a storage built in a computer to exhibit functions equivalent to the configuration of the information processing apparatus 10 described above. A computer-readable storage medium that records the program can also be provided.

<< 5. Conclusion >>
As described above, in the observation system 1 according to the present embodiment, in an environment where light (for example, skylight) including a band component absorbed by the target gas to be observed is irradiated, a low elevation angle and Spectral images are taken for each direction of high elevation angle. Next, the information processing apparatus 10 determines the optical thickness based on the ratio between the spectra indicating the intensity of the component for each wavelength in the band for each pixel between the spectral images corresponding to the directions of the low and high elevation angles. τ ′ _obs (λ) is calculated. Further, the information processing apparatus 10 calculates the simulated optical thickness τ ′ _sim (λ) based on the value of the absorption cross section of the target gas corresponding to the temperature at the time of observation. Then, the information processing apparatus 10 performs the fitting between the optical thickness τ ′ _obs (λ) calculated for each pixel and the simulated optical thickness τ ′ _sim (λ), so that the difference in target gas is obtained. The slant column concentration ΔSCD _g is calculated for each pixel.

With the configuration as described above, the information processing apparatus 10 according to the present embodiment calculates information indicating the spatial distribution of the target gas (that is, information indicating the differential slant column concentration ΔSCD _g calculated for each pixel). Is possible. Further, the information processing apparatus 10 according to the present embodiment outputs the output information (for example, an image as shown in FIG. 16) based on the information calculated as described above so that the spatial distribution of the target gas can be identified. Information) can be generated and presented to the user.

For reference, the Ministry of the Environment of Japan stipulates the following environmental standards for nitrogen dioxide (NO ₂ ) (environmental standards revised in 1996).
1 Environmental standards pertaining to nitrogen dioxide shall be as follows.
The daily average of hourly values is within or below the zone from 0.04 ppm to 0.06 ppm.
21 Environmental standards are measured values when measured by an absorptiometric method using Salzmann reagent or a chemiluminescent method using ozone in a place where it is recognized that the state of air pollution by nitrogen dioxide can be accurately grasped. According to.
31 Environmental standards of 1 do not apply to industrial areas, roadways or other areas or places where the general public does not normally live.

Here, in the example shown in FIGS. 4 and 16, the distance from the imaging device 20 to the building M11 is 3.6 km, and the SCD value (that is, the difference) of NO ₂ near the building M11 within the angle of view. It is assumed that the slant column concentration is 2 × 10 ¹⁷ mole / cm ² . At this time, the amount corresponding to the average concentration of NO ₂ is < _ng (l)> = 5.6 × 1011 molec./cm ³ , and assuming that the temperature is 10 ° C., the mixing ratio is calculated to be 0.022 ppm. . This value is lower than the environmental standard shown above. That is, according to the observation system 1 according to the present embodiment, it is possible to obtain NO ₂ concentration information even if the average contamination level is below.

  The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Observation system 10 Information processing apparatus 11 Analysis part 12 Spectral image 13 Output control part 20, 20a, 20b Imaging device 21 Reflection part 30 Storage part 50 Display apparatus

Claims (15)

A first image and a second image that are imaged at different elevation angles and in which the imaged times substantially coincide with each other in an environment irradiated with light including a component in a wavelength band that is absorbed by the target gas to be observed. An acquisition unit to acquire;
For each pixel corresponding between the first image and the second image, a first spectrum indicating the intensity of a component for each wavelength in the wavelength band in the pixel of the first image, and the second A first optical thickness corresponding to the pixel is calculated based on a ratio with a second spectrum indicating the intensity of a component for each wavelength in the wavelength band of the pixel of the image;
The target gas slant column corresponding to the pixel based on the first optical thickness calculated for each pixel and the second optical thickness calculated based on the absorption cross section of the target gas calculated in advance. An analysis unit for estimating the concentration;
Based on the slant column concentration estimated for each pixel, a generation unit that generates information indicating the concentration distribution of the target gas;
A first imaging unit that captures the first image;
A second imaging unit that captures the second image;
An information processing apparatus comprising:   The information processing apparatus according to claim 1, wherein the target gas is a gas having an absorption spectrum in a wavelength band of ultraviolet, visible, and near infrared.   The information processing apparatus according to claim 2, wherein the target gas is a gas having an optical thickness variation range of 0.01 or more for each wavelength. The target gas is nitrogen dioxide,
The first spectrum and the second spectrum include information indicating the intensity of the component for each wavelength in at least a part of the wavelength band of 400 to 500 nm,
The information processing apparatus according to claim 2 or 3. The target gas is carbon dioxide,
The first spectrum and the second spectrum include information indicating the intensity of a component for each wavelength in at least some of the wavelength bands of 1550 to 1600 nm,
The information processing apparatus according to claim 2 or 3.   The analysis unit according to any one of claims 1 to 5, wherein the analysis unit calculates the second optical thickness based on the absorption cross sections of the target gas and the oxygen dimer calculated in advance. The information processing apparatus described in 1.   The analysis unit calculates a pseudo transmittance based on an assumed value of a differential slant column concentration according to the absorption cross-sectional areas of the target gas and the oxygen dimer, and based on the pseudo transmittance, the second transmittance is calculated. The information processing apparatus according to claim 6, wherein the information processing apparatus calculates an optical thickness. The analysis unit
Sequentially changing the assumed value of the differential slant column concentration, and calculating the second optical thickness based on the pseudo transmittance according to the assumed value;
By comparing the second optical thickness calculated based on the pseudo transmittance for each hypothetical value and the first optical thickness calculated for each pixel, the first optical thickness is Searching for the second optical thickness approximately matching,
Based on the search result of the second optical thickness, estimate the slant column concentration of the target gas corresponding to the pixel,
The information processing apparatus according to claim 7.   The information processing apparatus according to claim 1, wherein the light is scattered light of sunlight.   Each of the said 1st image and the said 2nd image contains the information which shows the light intensity | strength of each of several wavelength bands based on the spectral result of the light from a to-be-photographed object as described in any one of Claims 1-9. The information processing apparatus described.   The information processing apparatus according to claim 1, wherein the generation unit generates a third image as information indicating a concentration distribution of the target gas. An imaging unit that captures an image within an angle of view;
An optical member for switching the imaging direction of the imaging unit;
Including
The imaging unit captures the first image and the second image in a time-sharing manner by switching the imaging direction by the optical member.
The information processing apparatus according to any one of claims 1 to 11. The acquisition unit acquires a still image for each frame as the first image and the second image from each of the first moving image and the second moving image captured at different elevation angles,
The analysis unit calculates the first optical thickness for each corresponding pixel between the first image and the second image acquired for each frame, and calculates the first optical thickness and the first optical thickness. Based on the second optical thickness, estimate the slant column concentration of the target gas corresponding to the pixel in the frame,
The generating unit generates information indicating a change along a time series of the concentration distribution of the target gas based on the slant column concentration estimated for each pixel for a plurality of frames.
The information processing apparatus according to any one of claims 1 to 12 . A first image and a second image that are imaged at different elevation angles and in which the imaged times substantially coincide with each other in an environment irradiated with light including a component in a wavelength band that is absorbed by the target gas to be observed. Getting,
Processor
For each pixel corresponding between the first image and the second image, a first spectrum indicating the intensity of a component for each wavelength in the wavelength band in the pixel of the first image, and the second Calculating a first optical thickness corresponding to the pixel based on a ratio with a second spectrum indicating the intensity of a component for each wavelength in the wavelength band in the pixel of the image;
The target gas slant column corresponding to the pixel based on the first optical thickness calculated for each pixel and the second optical thickness calculated based on the absorption cross section of the target gas calculated in advance. Calculating the concentration;
Generating information indicating a concentration distribution of the target gas based on the slant column concentration calculated for each pixel;
Including an information processing method. On the computer,
A first image and a second image that are imaged at different elevation angles and in which the imaged times substantially coincide with each other in an environment irradiated with light including a component in a wavelength band that is absorbed by the target gas to be observed. Getting,
For each pixel corresponding between the first image and the second image, a first spectrum indicating the intensity of a component for each wavelength in the wavelength band in the pixel of the first image, and the second Calculating a first optical thickness corresponding to the pixel based on a ratio with a second spectrum indicating the intensity of a component for each wavelength in the wavelength band in the pixel of the image;
The target gas slant column corresponding to the pixel based on the first optical thickness calculated for each pixel and the second optical thickness calculated based on the absorption cross section of the target gas calculated in advance. Calculating the concentration;
Generating information indicating a concentration distribution of the target gas based on the slant column concentration calculated for each pixel;
A program that executes