JP2021156660A - Measurement device and measurement method - Google Patents

Abstract

To enable a measurement of the number of particles or a size thereof existing in a prescribed area without affecting a measurement object, and what is more, to enable the measurement even if the prescribed area is remote.SOLUTION: A measurement device 1 comprises: a measurement unit 10 that radiates a prescribed area where a plurality of particles exist with transmission light comprised of pulse-like laser light, receives scattering light from each particle with respect to the transmitted light as reception light, and obtains a reception signal on the basis of the transmission light and received light; and a calculation unit 20 that obtains a Doppler spectrum on the basis of the reception signal obtained by the measurement unit 10, and calculates the number of particles and/or a size thereof existing in the prescribed area on the basis of a reception signal of each particle coming up on the obtained Doppler spectrum. The measurement unit 10 radiates transmission light comprised of laser light with a pulse length and a wavelength each having values enabling a speed of each particle to be discriminated on the basis of reception signal of each particle coming on the obtained Doppler spectrum.SELECTED DRAWING: Figure 1

Description

The present invention relates to a measuring device and a measuring method suitable for measuring the number density of fine particles in a remote region.

The particle counter is a measuring instrument that measures the number density of fine particles existing in the air or liquid (the size and number of fine particles present per unit volume of gas or liquid) (see Non-Patent Document 1). The particle counter is used for various purposes such as monitoring the cleanliness in a clean room and monitoring the air pollution level in an urban area. The measurement of the particle counter is to suck a unit volume of gas or liquid into the measuring unit of the apparatus, irradiate the sucked gas or liquid with laser light, and measure the amount of scattered and absorbed light by the fine particles. It is known that the amount of light scattered and absorbed by the fine particles depends on the ratio of the wavelength of the laser light to the particle size, and the number density of the fine particles can be calculated based on this known dependency.

In order to monitor the number density of local fine particles such as in a clean room, it is considered sufficient to use a conventional particle counter.

In addition, there are non-patent documents 2 and 3 as a technique related to the present invention.

https://www.rion.co.jp/product/docs/10.pdf 'Wind ranging and velocimetry with low peak power and long-duration modulated laser' Eiichi Yoshikawa and Tomoo Ushio, Vol. 25, No. 8 | 17 Apr 2017 | OPTICS EXPRESS 8845 van de Hulst, "Light Scattering by Small Particles," Dover.

However, since the conventional particle counter inhales gas or liquid, it affects the fine particles (density, etc.) to be observed. That is, the method of inhalation may affect the measurement result. In addition, in-situ observations such as conventional particle counters and in-situ observations at multiple points are not sufficient to know the overall degree of pollution of the atmosphere.

In view of the above circumstances, an object of the present invention is a case where the number and size of fine particles existing in a predetermined region can be measured without affecting the measurement target, and the predetermined region is remote. It is an object of the present invention to provide a measuring device and a measuring method capable of measuring even if it is.

In order to achieve the above object, the measuring device according to the present invention emits transmitted light composed of pulsed laser light to a predetermined region where a plurality of fine particles exist, and receives scattered light of each of the fine particles with respect to the transmitted light. A measuring unit that receives as light and obtains a received signal based on the transmitted light and the received light, and a Doppler spectrum obtained based on the received signal obtained by the measuring unit, and each of the above appearing on the obtained Doppler spectrum. A calculation unit for calculating the number and / or size of the fine particles in the predetermined region based on the received signal of the fine particles is provided, and the measuring unit includes each of the above based on the received signal of each of the fine particles in the Doppler spectrum. The transmitted light composed of laser light having a pulse length and a wavelength that can distinguish the velocities of the fine particles is emitted.

In the present invention, the measuring unit is configured to emit transmitted light consisting of laser light having a pulse length and wavelength that can distinguish the velocity of each particle based on the received signal of each particle appearing on the Doppler spectrum, and the calculation unit By calculating the number of received signals of each distinguishable fine particle appearing on the Doppler spectrum, the number of fine particles existing in a predetermined region and the number density can also be calculated. Further, in the present invention, the size of each fine particle in a predetermined region can be calculated from the size of the received signal of each fine particle that can be distinguished by the calculation unit appearing on the Doppler spectrum. As a result, the number and size of fine particles existing in a predetermined region can be measured without affecting the measurement target, and even when the predetermined region is remote, the measurement can be performed. In the present invention, as long as the laser beam reaches, it is possible to measure fine particles in a predetermined region not only in the air but also in the liquid.

In the measuring device according to one embodiment of the present invention, the measuring unit is based on the laser beam having a pulse length and wavelength at which the received signals of the fine particles having a velocity range appearing on the Doppler spectrum do not overlap on the Doppler spectrum. The transmitted light is emitted.

と表すことができる。ここで、ｔは時間、ｊは虚数単位、ｆｄはドップラ周波数偏移である。ｆｄの値は予め任意に決定することができ、参照信号に上記の関数を用いた場合、ドップラ周波数偏移ｆｄを有する信号を取り出すことができる。 In the measuring device according to one embodiment of the present invention, the calculation unit obtains a Doppler spectrum for each range by performing Doppler spectrogram processing on the received signal obtained by the measuring unit based on the reference signal. Then, the spatial distribution of the number and / or size of the fine particles existing in the predetermined region is calculated based on the reception signal of the fine particles of each range bin appearing on each of the obtained Doppler spectra. Here, when the reference signal is the transmission signal f (t),

It can be expressed as. Here, t is time, j is an imaginary unit, and fd is Doppler frequency shift. The value of fd can be arbitrarily determined in advance, and when the above function is used as the reference signal, a signal having a Doppler frequency deviation fd can be extracted.

In the measuring device according to one embodiment of the present invention, the measuring unit obtains a plurality of received signals for the plurality of wavelengths by using the pulsed laser light having a plurality of wavelengths, and the calculation unit is the measuring unit. A plurality of Doppler spectra are obtained based on the obtained plurality of received signals, and the number of the fine particles present in the predetermined region based on the received signals of the respective fine particles appearing on each of the obtained Doppler spectra. And / or calculate the size. Since the observation data at two different wavelengths are independent of each other, the influence of observation error is reduced, and the number and / or size of the fine particles existing in the predetermined region is calculated with higher accuracy than the observation at one wavelength. be able to. In addition, since the scattering characteristics of the fine particles depend on the size and type of the fine particles and are unique at each wavelength (see Non-Patent Document 3), it is possible to determine the type of the fine particles existing in the predetermined region. can. Basically, the scattering intensity at each wavelength (which can be converted from the received signal intensity appearing in the Doppler spectrum) can be converted into the size and type of fine particles. It should be noted that the accuracy improvement using the two wavelengths and the discrimination of the type of fine particles may not be compatible depending on the wavelength selection.
In the measuring device according to one embodiment of the present invention, the measuring unit emits the transmitted light composed of laser light having a wavelength that causes Raman scattering with respect to the fine particles for which it is desired to determine whether or not they are present in the predetermined region. The calculation unit further includes a discrimination unit that determines the presence or absence of Raman scattering based on the received light measured by the measurement unit.
The measuring device according to one embodiment of the present invention measures the number density or the number density and the type of fine particles existing in a remote air or liquid.
The measuring device according to one embodiment of the present invention uses a laser to measure the number density or the number density and type of fine particles existing in a remote air or liquid.
The measuring device according to one embodiment of the present invention uses a coherent laser to measure the number density or the number density and type of fine particles existing in a remote air or liquid.
The measuring device according to one embodiment of the present invention separates particles on a Doppler spectrum using a coherent laser and measures the number density or the number density and type of fine particles existing in a remote air or liquid.
The measuring device according to one embodiment of the present invention further measures the spatial distribution of the number density or the number density and type of fine particles present in a remote air or liquid.
In the measurement method according to one embodiment of the present invention, transmission light composed of pulsed laser light is emitted to a predetermined region, and scattered light of each fine particle in the predetermined region with respect to the transmission light is received as reception light. A reception signal is obtained based on the transmission light and the reception light, a Doppler spectrum is obtained based on the obtained reception signal, and the above-mentioned existing in the predetermined region based on the reception signal of each of the fine particles appearing on the Doppler spectrum. It is a measurement method for calculating the number and / or size of fine particles, and consists of laser light having a pulse length and wavelength that can distinguish the velocity of each fine particle based on the received signal of each fine particle appearing on the Doppler spectrum. The transmitted light is emitted.

According to the present invention, the number, size, and type of fine particles existing in a predetermined region can be measured without affecting the measurement target, and even when the predetermined region is remote, the measurement can be performed. be able to.

It is a block diagram which shows the structure of the measuring apparatus which concerns on one Embodiment of this invention. It is a figure for demonstrating the measuring method by the measuring apparatus which concerns on one Embodiment of this invention. It is a schematic diagram for demonstrating the outline of the number density measurement of the fine particles which concerns on this invention as compared with the general rider method.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a configuration of a measuring device according to an embodiment of the present invention.
As shown in FIG. 1, the measuring device 1 includes a measuring unit 10, a calculation unit 20, and a display 30.

As shown in FIG. 2, the measuring device 1 radiates transmitted light composed of pulsed laser light to a predetermined region 2 which is typically a remote measurement target, and is reflected light of the emitted laser light. The scattered light of a plurality of fine particles existing in a predetermined region 2 is received as received light, and a received signal for calculating the number of fine particles or the like is output using the received light.

The measuring unit 10 emits transmitted light composed of laser light having a pulse length and wavelength that can distinguish the received signal of each fine particle through Doppler spectrum processing described later.

The calculation unit 20 distinguishes the received signal of each fine particle through Doppler spectrum processing, and calculates the number density of the fine particles from the number and size of the received signals.

The measuring unit 10 includes an optical oscillator 11, an optical coupler 12, an optical modulator 13, an optical amplifier 18, an optical circulator 14, an optical system 15, an optical coupler 16, an optical receiver 17, and an arbitrary signal generator. Has 19 and.

The optical oscillator 11 is an optical oscillator that oscillates a laser beam, which is typically a coherent laser, and is connected to an optical coupler 12 to output the oscillated laser beam to the optical coupler 12. For example, a semiconductor laser, a solid-state laser, or the like is used for the optical oscillator 11.

The optical coupler 12 distributes the laser light oscillated by the optical oscillator 11 into the transmission light and the local light, outputs the transmitted light to the light modulator 13, and outputs the local light to the optical receiver 17. The local light represents light passing through a path connected to the optical receiver 17 via the optical coupler 12, and the transmitted light is a path connected from the optical coupler 12 to the optical system 15 via the light modulator 13 and the optical amplifier 18. Represents the light that passes through. The optical coupler 12 is connected to an optical oscillator 11, an optical modulator 13, and an optical coupler 16, and outputs local light to the optical coupler 16 and outputs transmitted light to the optical modulator 13. For example, as the optical coupler 12, a molten fiber coupler, a filter type coupler using a dielectric multilayer filter, or the like is used.

The arbitrary signal generator 19 generates an arbitrary modulated signal. Here, the modulation includes pulse modulation, amplitude modulation, frequency modulation, and phase modulation.

The light modulator 13 modulates the transmitted light output by the optical coupler 12 using the modulated signal from the arbitrary signal generator 19. The light modulator 13 performs pulse modulation, amplitude modulation, frequency modulation, phase modulation, and the like on the transmitted light. The light modulator 13 is connected to the optical circulator 14 via an optical amplifier 18. The optical modulator 13 is composed of, for example, an optical modulator such as an AOM (Acousto-Optic Modulator), and outputs a pulse by pulse-modulating the transmitted light output from the optical coupler 12.
The optical amplifier 18 amplifies the pulse (laser light) output from the light modulator 13.

The optical circulator 14 outputs the pulse output from the optical amplifier 18 to the optical system 15, while outputting the received light, which is the reflected light of the pulse received by the optical system 15, to the optical coupler 16. For example, as the optical circulator 14, a space propagation type or a fiber coupling type is used, such as a circulator configured by using a wave plate and a beam splitter.

The optical system 15 radiates the pulse output from the optical circulator 14 to the atmosphere, and then receives the reflected light of the pulse reflected back in the predetermined region 2 to be measured. The optical system 15 is connected to the optical circulator 14. For example, an optical telescope is used for the optical system 15.

The optical coupler 16 combines the local light output from the optical coupler 12 with the received light output from the optical circulator 14 and outputs an optical signal to the optical receiver 17. For example, as the optical coupler 16, a molten fiber coupler, a filter type coupler using a dielectric multilayer filter, or the like is used.

The optical receiver 17 has a frequency obtained by combining the local light output from the optical coupler 12 and the received light output from the optical circulator 14 with the coupler and adding the frequency of the local light and the frequency of the received light. Converts combined light into an electrical signal. The optical receiver 17 is composed of, for example, a balanced receiver, converts the combined light output from the optical coupler 12 into an electric signal, and outputs the electric signal as a reception signal to the calculation unit 20.

The calculation unit 20 obtains a Doppler spectrum based on the received signal obtained by the measuring unit 10, and based on the received signal of each fine particle appearing on the obtained Doppler spectrum, determines the number density of fine particles in a predetermined region 2 and the like. calculate.

The calculation unit 20 includes an A / D conversion unit 21 and a Doppler spectrum processing unit 22.

The A / D conversion unit 21 converts the received electrical signal as a reception signal output from the optical receiver 17 into a digital signal, and outputs the signal to the Doppler spectrum processing unit 22.

The Doppler spectrum processing unit 22 obtains a Doppler spectrum by performing a Fourier transform process, and counts the number of received signals of each fine particle appearing on the Doppler spectrum to increase the number of fine particles existing in a predetermined region 2 and further. Also calculates the number density, and calculates the size of each fine particle from the size of the received signal of each fine particle appearing on the Doppler spectrum.

The display 30 displays the measurement result, which is the calculation result by the calculation unit 20, on the screen.

In the measuring device 1 according to the present embodiment, a new rider method different from the conventional general rider method is adopted in order to obtain the above number density and the like. The new rider method will be described while comparing this point with the general rider method. The outline diagram is shown in FIG.

The general rider method radiates a coherent light pulse into the air and receives scattered light of fine particles with respect to the synchrotron radiation. The scattered light is the synchrotron radiation shifted in Doppler frequency, and the Doppler frequency shift corresponds to the relative velocity of the fine particles with respect to the rider. A Doppler spectrum can be obtained by extracting a signal with an arbitrary delay time and time width from the received signal and performing a Fourier transform. The delay time corresponds to the measured distance, the time width corresponds to the measured volume, and the Doppler spectrum is the distribution regarding the velocity of the received signal intensity of each fine particle at that distance / volume (see FIG. 3 (a)). .. Since the received signal of one fine particle has a constant velocity range on the Doppler spectrum, the received signals of a plurality of fine particles appear overlapping. In general, it is not possible to separate the received signal of each of the overlapping fine particles, and the average speed of the entire fine particles is obtained. The average velocity of the particles is consistent with the wind speed.

While the general rider method uses a short-time optical pulse of a single frequency, the new rider method uses a modulated long-time optical pulse (a sufficient long-time pulse corresponds to a continuous wave). According to the research by the present inventors described in Non-Patent Document 2, it was found that the width Δv of the received signal of one fine particle appearing in the Doppler spectrum is inversely proportional to the pulse length according to the following equation.
Δv = cλ / 2T
Here, c is the speed of light, λ is the wavelength of the laser, and T is the pulse length. Since each fine particle has a slight speed difference, the received signals of each fine particle can be separated (non-overlapping) by sufficiently increasing the pulse length and reducing the speed width of the received signal. It is possible. As a result, each fine particle appears with an independent peak on the Doppler spectrum (see FIG. 3B), and the size and number of fine particles can be obtained from the intensity and number of each received signal.

The measuring device 1 according to the present embodiment adopts a new rider method. That is, the measuring unit 10 has a pulse length T and a wavelength at which the received signals (indicated by the reference numerals s in FIG. 3B) of the fine particles having a velocity width Δv appearing on the Doppler spectrum do not overlap on the Doppler spectrum. It emits transmitted light consisting of λ laser light. That is, the wavelength λ of the laser light and the pulse length T are selected as the transmitted light so that the velocity width Δv becomes sufficiently small with respect to the velocity difference of the fine particles. For example, when a rider using an infrared laser beam of 1500 nm uses an optical pulse having a pulse length of 500 μsec, the theoretical velocity width of the received signal of one fine particle appearing on the Doppler spectrum is 0.0075 m / sec.

Since the conventional particle counter inhales gas or liquid, there is a possibility that the fine particles (density, etc.) to be measured may be affected. On the other hand, in the measuring device 1 according to the present embodiment, since the fine particles to be measured are only irradiated with the laser beam, the measurement can be performed without affecting the measurement target. Further, for example, in order to know the overall degree of pollution of the atmosphere, it cannot be said that in-situ observation like a conventional particle counter or in-situ observation is performed at multiple points. On the other hand, in the measuring device 1 according to the present embodiment, since the measurement is performed by the rider, the measurement can be performed even when the distance is remote, and the overall degree of pollution of the atmosphere can be easily measured. This is expected to make the measurement of air pollution such as PM2.5 and yellow sand more accurate, and may be utilized as a standard method for pollution degree verification. In addition, it is expected that a wide economic ripple effect will be produced through global environmental measurement, such as the possibility of obtaining knowledge such as advection of pollutants.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made.

For example, the calculation unit 20 obtains a Doppler spectrum for each range bin based on the reception signal obtained by the measurement unit 10, and determines a predetermined region 2 based on the reception signal of each fine particle of each range bin appearing on each obtained Doppler spectrum. It may be configured to calculate the spatial distribution of the number and / or size of fine particles present in.

Further, by measuring the laser light of a plurality of wavelengths at each wavelength by the new rider method, it is possible to utilize the difference in the scattered light between the wavelengths. This is because the measurement unit 10 shares the optical system 15 and has other configurations other than the optical system 15 of the measurement unit 10 for each wavelength, and the calculation unit 20 for each wavelength received signal. Perform Doppler spectrum processing. Further, the calculation unit 20 determines that the received signals having the same velocity are the same particles in the plurality of Doppler spectra obtained by the plurality of wavelengths, and determines the type of the particles from the difference in the received signal intensity between the wavelengths and the like. Perform the processing to be performed.

Further, by generating Raman scattering for specific fine particles using a laser having a specific wavelength, it is possible to measure the number density of the fine particles and determine the type of the fine particles at the same time. In this case, the measurement unit 10 is configured to emit transmitted light composed of laser light having a wavelength that causes Raman scattering to the fine particles for which it is desired to determine whether or not they are present in the predetermined region 2, and the calculation unit 20 is configured to emit Raman scattering. Doppler spectrum processing is performed on the received signal obtained at the wavelength at which the above occurs. In the obtained Doppler spectrum, only the received signal from the particle that generated Raman scattering appears. The calculation unit 20 may calculate the number density of the fine particles from the number of received signals on the Doppler spectrum. Furthermore, the new rider method measurement may be performed at a plurality of wavelengths by simultaneously using a wavelength that causes Raman scattering for specific fine particles and a wavelength that does not. As a result, the accuracy of measuring the number density of specific fine particles is further improved.

Further, the measuring device according to the present invention can perform a wider range of fine particle measurement without burden by providing, for example, a mechanism in which the optical system in the measuring unit scans at an azimuth angle and / or an elevation angle.

Furthermore, the measuring device according to the present invention can be used not only for measuring air pollution but also for measuring fine particles in a region such as chimney dust that cannot be reached by humans. In addition, the measuring device according to the present invention can also be used for applications such as meteorological observation.

1: Measuring device 2: Area 10: Measuring unit 11: Optical oscillator 12: Optical coupler 13: Optical modulator 14: Optical circulator 15: Optical system 16: Optical coupler 17: Optical receiver 18: Optical amplifier 19: Arbitrary signal generation Unit 20: Calculation unit 21: A / D conversion unit 22: Spectrogram processing unit 30: Display

Claims (11)

Transmitted light composed of pulsed laser light is radiated to a predetermined region where a plurality of fine particles are present, scattered light of each of the fine particles with respect to the transmitted light is received as received light, and received based on the transmitted light and the received light. The measuring unit that obtains the signal and
A Doppler spectrum is obtained based on the received signal obtained by the measuring unit, and the number and / or size of the fine particles in the predetermined region is obtained based on the received signal of each of the fine particles appearing on the obtained Doppler spectrum. It is equipped with a calculation unit that calculates
The measuring unit is a measuring device that emits the transmitted light composed of a laser beam having a pulse length and a wavelength at which the velocity of each fine particle can be distinguished based on a received signal of each fine particle appearing on the Doppler spectrum. The measuring device according to claim 1.
The measuring unit is a measuring device that emits the transmitted light composed of a laser beam having a pulse length and a wavelength at which the received signals of the fine particles having a velocity width appearing on the Doppler spectrum do not overlap on the Doppler spectrum. The measuring device according to any one of claims 1 or 2.
The calculation unit obtains a Doppler spectrum for each range based on the reference signal with respect to the received signal obtained by the measurement unit, and each of the fine particles of each range bin appearing on each of the obtained Doppler spectra. A measuring device that calculates the spatial distribution of the number and / or size of the fine particles existing in the predetermined region based on the received signal. The measuring device according to any one of claims 1 to 3.
The measuring unit obtains a plurality of received signals for the plurality of wavelengths by using the pulsed laser light having a plurality of wavelengths, and obtains the plurality of received signals for the plurality of wavelengths.
The calculation unit obtains a plurality of Doppler spectra based on the plurality of received signals obtained by the measuring unit, and the predetermined one is based on the received signals of the respective fine particles appearing on the obtained Doppler spectra. A measuring device that calculates the number and / or size of the fine particles existing in the region and determines the type of the fine particles. The measuring device according to any one of claims 1 to 4.
The measuring unit emits the transmitted light composed of laser light having a wavelength that causes Raman scattering with respect to the fine particles for which it is desired to determine whether or not they are present in the predetermined region.
The calculation unit is a measuring device further including a discriminating unit that determines the presence or absence of Raman scattering based on the received light measured by the measuring unit. A measuring device that measures the number density or the number density and type of fine particles existing in a remote air or liquid. The measuring device according to claim 6.
A measuring device that uses a laser to measure the number density or number density and type of fine particles present in a remote air or liquid. The measuring device according to claim 7.
A measuring device that uses a coherent laser to measure the number density or number density and type of fine particles present in a remote air or liquid. The measuring device according to claim 8.
A measuring device that separates particles on a Doppler spectrum using a coherent laser and measures the number density or number density and type of fine particles present in a remote air or liquid. The measuring device according to claims 6 to 9, further
A measuring device that measures the spatial distribution of the number density or number density and type of fine particles present in a remote air or liquid. Transmitted light consisting of pulsed laser light is radiated to a predetermined area,
The scattered light of each fine particle in the predetermined region with respect to the transmitted light is received as the received light, and the light is received.
Obtaining a received signal based on the transmitted light and the received light,
A Doppler spectrum was obtained based on the obtained received signal.
A measurement method for calculating the number and / or size of the fine particles existing in the predetermined region based on the received signal of the fine particles appearing on the Doppler spectrum.
A measuring method for emitting the transmitted light composed of a laser beam having a pulse length and a wavelength at which the velocity of each fine particle can be distinguished based on a received signal of each fine particle appearing on the Doppler spectrum.

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