WO2020241212A1 - Aerosol measurement device and aerosol measurement method - Google Patents

Abstract

According to one mode of the present invention, the aerosol measurement device (1) comprises: a light source (20); a first etalon (10) wherethrough a first light (L1) which has been emitted from the light source passes; a second etalon (15) wherethrough a second light (L3) which has been scattered by an aerosol (90) contained in the atmosphere passes; and a control unit (70) changing at least one light path length selected from the group consisting of the light path length of the first light in the first etalon and the light path length of the second light in the second etalon.

Description

Aerosol measuring device and aerosol measuring method

The present disclosure relates to an aerosol measuring device and an aerosol measuring method.

Conventionally, a technique for measuring aerosols in the atmosphere using a lidar (LIDAR: Light Detection and Ringing) is known. The lidar is a technique for observing aerosols floating in the air such as yellow sand, pollen, dust, or minute water droplets by measuring and analyzing the scattered light of pulsed light emitted into the atmosphere.

The scattered light usually includes Mie scattered light and Rayleigh scattered light. The Mie scattered light is scattered light generated by Mie scattering, which is a scattering phenomenon caused by fine particles having a particle size equal to or larger than the wavelength of the emitted light. The Mie scattered light is, for example, scattered light from an aerosol which is an object to be measured. Rayleigh scattering is a scattering phenomenon caused by fine particles and atmospheric molecules smaller than the wavelength of emitted light. By excluding Rayleigh scattered light from scattered light, Mie scattered light can be obtained.

For example, Patent Document 1 discloses a technique for spectroscopically separating scattered light from a single laser beam into Mie scattered light and Rayleigh scattered light using a filter. Further, for example, in Patent Document 2, an interferometer that selectively transmits light having the same spectral interval as the emitted laser light by utilizing the fact that the mode interval of the spectrum of the laser beam in the multi-longitudinal mode is constant. A technique for dispersing scattered light using a laser is disclosed.

International Publication No. 2003/073127 Japanese Patent No. 6243088

However, in the above-mentioned conventional technique, when the peak wavelength of the laser beam changes due to a temperature change or the like, it is necessary to synchronize the optical path difference while sweeping one wavelength of the laser beam. Therefore, there is a problem that a structure for making the optical path difference variable is required, the device becomes large, and the measurement method becomes complicated.

Therefore, the present disclosure provides an aerosol measuring device and an aerosol measuring method capable of easily and accurately measuring an aerosol.

The aerosol measuring device according to one aspect of the present disclosure is a device for measuring aerosol contained in the atmosphere. The aerosol measuring device according to one aspect of the present disclosure includes a light source, a first etalon through which the first light emitted from the light source passes, and a second etalon through which the second light scattered by the aerosol passes. An etalon and a control unit that changes at least one optical path length selected from the group consisting of the optical path length of the first light in the first etalon and the optical path length of the second light in the second etalon. , Equipped with.

Further, in the aerosol measurement method according to one aspect of the present disclosure, the first light emitted from the light source is incident on the first etalon, and the light emitted from the first etalon is included in the atmosphere. Irradiating the aerosol, making the second light scattered by the aerosol incident on the second etalon, and in the optical path length of the first light in the first etalon and in the second etalon. Including changing at least one optical path length selected from the group consisting of the optical path length of the second light.

Further, one aspect of the present disclosure can be realized as a program for causing a computer to execute the above aerosol measurement method. Alternatively, it can be realized as a computer-readable non-temporary recording medium in which the program is stored.

According to the present disclosure, aerosols can be measured easily and accurately.

FIG. 1 is a diagram showing a configuration of an aerosol measuring device according to the first embodiment. FIG. 2 is a flowchart showing the operation of the aerosol measuring device according to the first embodiment. FIG. 3 is a diagram showing an example of the spectrum of the multi-laser light emitted by the aerosol measuring device according to the first embodiment. FIG. 4 is a diagram for explaining the 0th transmitted light and the 1st transmitted light passing through the optical element of the aerosol measuring device according to the first embodiment. FIG. 5 is a diagram for explaining the 0th transmitted light and the 2nd transmitted light passing through the optical element of the aerosol measuring device according to the first embodiment. FIG. 6 is a diagram showing an example of a spectrum of scattered light generated by scattering the multi-laser light emitted by the aerosol measuring device according to the first embodiment. FIG. 7 is a diagram showing a calculation result of an interferogram when scattered light including Mie scattered light and Rayleigh scattered light is interfered with by a Michelson interferometer. FIG. 8 is an enlarged view of a part of FIG. 7. FIG. 9 is a diagram for explaining the dependence of the frequency interval of the interference fringe by the Michelson interferometer when there is no scattering by the aerosol and only the atmospheric scattering is considered. FIG. 10 is a diagram showing the frequency characteristics of the transmittances of two etalons having different optical path lengths. FIG. 11 is a diagram showing an example of a change in the optical path length of the etalon by the aerosol measuring device according to the first embodiment. FIG. 12 is a diagram showing the relationship between the temperature difference of etalon and the intensity of emitted light. FIG. 13 is a diagram showing a configuration of an aerosol measuring device according to the second embodiment. FIG. 14 is a diagram showing an example of a change in the optical path length of the etalon by the aerosol measuring device according to the second embodiment. FIG. 15 is a diagram showing the relationship between the inclination of the optical axis of Etalon and the intensity of emitted light. FIG. 16 is a diagram showing a configuration of an aerosol measuring device according to a third embodiment. FIG. 17 is a diagram showing a configuration of an aerosol measuring device according to a fourth embodiment. FIG. 18 is a diagram for explaining the operation of the light-shielding portion of the aerosol measuring device according to the fourth embodiment.

(Summary of this disclosure)
The aerosol measuring device according to one aspect of the present disclosure is a device for measuring aerosol contained in the atmosphere. The aerosol measuring device according to one aspect of the present disclosure includes a light source, a first etalon through which the first light emitted from the light source passes, and a second light through which the second light scattered by the aerosol passes. An etalon and a control unit that changes at least one optical path length selected from the group consisting of the optical path length of the first light in the first etalon and the optical path length of the second light in the second etalon. , Equipped with.

The first etalon irradiates the aerosol with interference light having a plurality of peaks separated from each other at equal frequency intervals, which is generated by internally interfering the first light, and the second etalon is produced. , The Mie scattered light may be emitted by interfering the second light internally.

The aerosol measuring device according to one aspect of the present disclosure may further include a receiver that receives the Mie scattered light.

As a result, light can be interfered with by the first etalon and the second etalon, respectively, so that the number of parts can be reduced as compared with the case of using a Michelson interferometer, and the configuration of the aerosol measuring device can be simplified. Can be. Further, since the Rayleigh scattered light can be removed by the second etalon, the aerosol can be easily measured based on the light receiving intensity by the light receiver without requiring complicated signal processing.

Further, even if there is a difference in the optical characteristics between the first etalon and the second etalon due to manufacturing variation or operation variation, the optical path length of the first light in the first etalon and the first in the second etalon. Since at least one optical path length selected from the group consisting of two optical path lengths can be changed, the peak positions in the frequency characteristics of the transmittances of the first etalon and the second etalon are tuned. Can be done. Note that tuning is to match the peak positions. By synchronizing the peak positions, it is possible to allow the receiver to receive Mie scattered light of sufficient intensity while sufficiently suppressing the transmission of Rayleigh scattered light. As a result, the measurement accuracy of the aerosol can be improved.

Further, for example, the control unit may change the optical path length of the second light in the second etalon.

As a result, the optical path length of the first light in the first etalon can be kept constant, so that the configuration and control for changing the optical path length can be simplified.

Further, for example, the control unit may periodically change the at least one optical path length within a predetermined range.

As a result, by periodically changing the optical path length within a predetermined range, it is possible to easily measure the aerosol with an appropriate optical path length for synchronizing the peak position. Further, even when the optical path lengths of the two etalons change due to the operation variation, the aerosol can be easily measured with an appropriate optical path length for synchronizing the peak positions.

Further, for example, the frequency interval may be 3.9 GHz or less.

As a result, Etalon can sufficiently suppress the transmission of Rayleigh scattered light, so that the receiver can receive Mie scattered light based on the aerosol. Therefore, the presence / absence and concentration of aerosol can be easily measured based on the intensity of light received by the light receiver.

Further, for example, the aerosol measuring device according to one aspect of the present disclosure further includes a temperature adjusting device that adjusts at least one selected from the group consisting of the temperature of the first etalon and the temperature of the second etalon. In addition, the control unit may change the at least one optical path length by controlling the temperature adjusting device.

As a result, the optical path length can be easily changed by utilizing the thermal expansion and contraction of etalon.

Further, for example, the aerosol measuring device according to one aspect of the present disclosure further comprises at least one selected from the group consisting of the inclination of the optical axis of the first etalon and the inclination of the optical axis of the second etalon. A shaft adjusting device for adjusting is provided, and the control unit may change the at least one optical path length by controlling the shaft adjusting device.

As a result, the optical path length of the etalon can be easily changed by tilting the optical axis of the etalon with respect to the incident direction of the light.

Further, for example, the first light is pulsed light, and the receiver receives the Mie from the time when the pulsed light is emitted from the light source until the end of a predetermined period longer than the time width of the pulsed light. The Mie scattered light may be received after the reception of the scattered light is stopped and the predetermined period is completed.

As a result, it is possible to suppress false detection of aerosol due to reflected light and failure due to saturation of the receiver.

Further, for example, the second light may enter the second etalon from an oblique direction with respect to the optical axis of the second etalon.

Thereby, the optical path length can be changed by adjusting the incident angle of the second light which is scattered light.

Further, for example, the light source may be a laser element or a light emitting diode (LED: Light Emitting Diode).

As a result, even if the intensity is attenuated by etalon, sufficient intensity of emitted light can be emitted toward the aerosol.

Further, for example, the aerosol measuring device according to one aspect of the present disclosure may further include a condensing unit that condenses the second light and causes it to be incident on the second etalon.

This makes it possible to increase the interference efficiency within the etalon. Moreover, since the light receiving sensitivity can be increased, the measurement accuracy of the aerosol can be improved.

Further, for example, in the aerosol measurement method according to one aspect of the present disclosure, the first light emitted from the light source is incident on the first etalon, and the light emitted from the first etalon is brought into the atmosphere. To irradiate the aerosol contained in the above, to make the second light scattered by the aerosol incident on the second etalon, and to make the optical path length of the first light in the first etalon and the second light. Includes changing at least one optical path length selected from the group consisting of said second light path lengths in etalon.

As a result, the aerosol can be measured easily and accurately in the same manner as the aerosol measuring device described above.

In the present disclosure, all or part of a circuit, unit, device, member or part, or all or part of a functional block in a block diagram, is a semiconductor device, a semiconductor integrated circuit (IC), or an LSI (Large Scale Integration). It may be executed by one or more electronic circuits including. The LSI or IC may be integrated on one chip, or may be configured by combining a plurality of chips. For example, functional blocks other than the storage element may be integrated on one chip. Here, it is called LSI or IC, but the name changes depending on the degree of integration, and it may be called system LSI, VLSI (Very Large Scale Integration), or ULSI (Ultra Large Scale Integration). Field Programmable Gate Array (FPGA), which is programmed after the manufacture of the LSI, or reconfigurable logistic device, which can reconfigure the junction relationship inside the LSI or set up the circuit partition inside the LSI, can also be used for the same purpose.

Furthermore, all or part of the functions or operations of circuits, units, devices, members or parts can be executed by software processing. In this case, the software is recorded on one or more ROMs, optical discs, non-temporary recording media such as hard disk drives, and when the software is executed by a processor, the functions identified by the software It is executed by a processor and peripheral devices. The system or device may include one or more non-temporary recording media on which the software is recorded, a processor, and the required hardware device, such as an interface.

Hereinafter, the embodiment will be specifically described with reference to the drawings.

It should be noted that all of the embodiments described below show comprehensive or specific examples. The numerical values, shapes, materials, components, arrangement positions and connection forms of the components, steps, the order of steps, etc. shown in the following embodiments are examples, and are not intended to limit the present disclosure. Further, among the components in the following embodiments, the components not described in the independent claims will be described as arbitrary components.

In addition, each figure is a schematic view and is not necessarily exactly illustrated. Therefore, for example, the scales and the like do not always match in each figure. Further, in each figure, substantially the same configuration is designated by the same reference numerals, and duplicate description will be omitted or simplified.

Further, in the present specification, terms indicating relationships between elements such as parallel or vertical, terms indicating the shape of elements such as cylinders or prisms, and numerical ranges are not expressions expressing only strict meanings. , Is an expression meaning that a substantially equivalent range, for example, a difference of about several percent is included.

(Embodiment 1)
[1. Constitution]
First, an outline of the aerosol measuring device according to the first embodiment will be described with reference to FIG. FIG. 1 is a diagram showing a configuration of an aerosol measuring device 1 according to the present embodiment.

As shown in FIG. 1, the aerosol measuring device 1 according to the present embodiment emits the emitted light L2 into the atmosphere, and the scattering body 90 existing in the atmosphere scatters the emitted light L2 to generate scattering. By acquiring the light L3 and processing the acquired scattered light L3, the presence / absence and concentration of the aerosol contained in the scatterer 90 are measured. The scatterer 90 exists in the target space for measurement by the aerosol measuring device 1.

The target space is, for example, a room in a building such as a residence, office, long-term care facility, or hospital. The target space is, for example, a space partitioned by walls, windows, doors, floors, ceilings, etc., and is a closed space, but is not limited to this. The target space may be an outdoor open space. Further, the target space may be the internal space of a moving body such as a bus or an airplane.

The scatterer 90 includes an aerosol to be measured, machined dust, coarse particles, and molecules constituting air. Specifically, the aerosol is dust floating in the target space, suspended particulate matter such as PM2.5, biological particles, or minute water droplets. Biological particles also include molds or mites floating in the air, pollen, and the like. In addition, minute water droplets include substances dynamically generated from the human body such as coughing or sneezing.

Aerosol, which is the object to be measured, is sufficiently large compared to the molecules that make up air. In the present embodiment, since the particle size of the aerosol is equal to or larger than the wavelength of the emitted light L2, the aerosol scatters the emitted light L2 to generate Mie scattered light. Since the molecules constituting the air are sufficiently smaller than the wavelength of the emitted light L2, Rayleigh scattered light is generated by scattering the emitted light L2. Therefore, the scattered light L3 acquired by the aerosol measuring device 1 includes Mie scattered light and Rayleigh scattered light. The Mie scattered light here is backscattered light due to Mie scattering. The aerosol measuring device 1 according to the present embodiment extracts Mie scattered light from the scattered light L3, and measures the presence / absence and concentration of the aerosol based on the extracted Mie scattered light.

The aerosol measuring device 1 according to the present embodiment emits emitted light L2 in different directions in the target space. The emission direction of the emitted light L2 is changed by, for example, a MEMS (Micro-Electro-Mechanical Systems) mirror (not shown). Alternatively, the emission direction of the emitted light L2 may be changed by changing the direction of the entire aerosol measuring device 1. The aerosol measuring device 1 can create an aerosol distribution in the target space by scanning the target space with the emitted light L2.

As shown in FIG. 1, the aerosol measuring device 1 includes an etalon 10 and 15, a light source 20, a mirror 22, a condensing unit 30, a condensing lens 40, a receiver 50, an analysis unit 60, and the like. It includes a control unit 70 and a heater 80. An example of the condensing unit 30 is a condensing lens 30a. Hereinafter, each component included in the aerosol measuring device 1 will be described.

Etalon 10 is a first etalon that interferes with incident light internally and emits as light having a plurality of peaks separated from each other at equal frequency intervals. Light having a plurality of peaks is also called multi-light. In this embodiment, the etalon 10 is a single etalon. That is, the etalon 10 is one member integrally configured. The shape of the etalon 10 is, for example, a cylinder or a prism.

As shown in FIG. 1, the etalon 10 has a translucent portion 11 and two multilayer films 12 and 13. The translucent portion 11 is formed by using a transparent material such as quartz or quartz. The translucent portion 11 is sandwiched between the two multilayer films 12 and 13, and is in contact with each of the two multilayer films 12 and 13. The two multilayer films 12 and 13 are dielectric multilayer films having a laminated structure of a plurality of dielectric films, respectively. For example, the two multilayer films 12 and 13 are each formed by alternately laminating a dielectric film having a low refractive index and a dielectric film having a high refractive index. As the dielectric film, for example, a titanium oxide film, a hafnium oxide film, a silicon oxide film, or the like is used. The light transmitting portion 11 may be an air layer, and the two multilayer films 12 and 13 may be fixed by a frame or the like so as to maintain a constant distance.

The emitted light L1 emitted from the light source 20 is incident on the etalon 10. The etalon 10 internally interferes with the emitted light L1 and emits as emitted light L2 which is light having a plurality of peaks separated from each other at equal frequency intervals. The emitted light L2 is a multi-laser light. In the present embodiment, the emitted light L1 is incident on the multilayer film 12 of the etalon 10 and emitted from the multilayer film 13. The surface of the multilayer film 12 opposite to the surface in contact with the translucent portion 11 is an incident surface on which the emitted light L1 is incident. The surface of the multilayer film 13 opposite to the surface in contact with the translucent portion 11 is an exit surface from which the emitted light L2 is emitted.

The etalon 15 is an example of a second etalon in which the scattered light L3 is internally interfered with and the Mie scattered light L4 contained in the scattered light L3 is passed through. Like the etalon 10, the etalon 15 internally interferes with the incident light and emits the light as light having a plurality of peaks separated from each other at equal frequency intervals. Etalon 15 and Etalon 10 have the same optical properties. That is, when the same light is incident on each of the etalons 10 and 15, the frequency intervals of the light emitted from each are the same. In this embodiment, the etalon 15 is a single etalon. That is, the etalon 15 is one member integrally configured. The shape of the etalon 15 is, for example, a cylinder or a prism.

As shown in FIG. 1, the etalon 15 has a translucent portion 16 and two multilayer films 17 and 18. The translucent portions 16 and the multilayer films 17 and 18 correspond to the translucent portions 11 and the multilayer films 12 and 13 of the etalon 10, respectively, and have the same configuration.

The scattered light L3 condensed by the condenser lens 30a is incident on the etalon 15. In the present embodiment, the scattered light L3 is incident from the multilayer film 17 of the etalon 15, and the Mie scattered light L4, which is a part of the scattered light L3, is emitted from the multilayer film 18. The surface of the multilayer film 17 opposite to the surface in contact with the translucent portion 16 is an incident surface on which scattered light L3 is incident. The surface of the multilayer film 18 opposite to the surface in contact with the light transmitting portion 16 is an exit surface from which Mie scattered light L4 is emitted.

Since the scattered light L3 includes light having a plurality of peaks separated from each other at equal frequency intervals, each light causes interference when passing through the etalon 15. In the present embodiment, the thickness of the etalon 15 is adjusted so that the Mie scattered light L4 contained in the scattered light L3 is passed and the Rayleigh scattered light is suppressed from passing. As a result, the Rayleigh scattered light can be appropriately removed from the scattered light L3, so that the Mie scattered light L4 caused by the aerosol can be received by the receiver 50.

In the present embodiment, the etalon 10 and the etalon 15 are arranged with a gap between them. Specifically, the etalon 10 is located on the optical path of the emitted light L1 emitted from the light source 20. More specifically, the etalon 10 is located between the mirror 22 and the opening provided in the outer housing of the aerosol measuring device 1. The opening is provided for the emission light L2 emitted from the etalon 10 to pass through.

Etalon 15 is located on the optical path of the scattered light L3 generated from the scattering body 90. Specifically, the etalon 15 is located between the condenser lens 30a and the condenser lens 40.

The light source 20 emits the emitted light L2 into the atmosphere via the etalon 10. Specifically, the light source 20 emits the emitted light L1. The emitted light L1 is, for example, pulsed light, but may be continuous light. The emitted light L1 may be monochromatic light having a peak in a specific wavelength band, or light containing a component in a broad wavelength band. The peak bandwidth is, for example, in the range of 10 pm to 10 nm. The emitted light L1 is, for example, ultraviolet light, blue light, infrared light, or the like. The emitted light L1 is reflected by the mirror 22 and then enters the etalon 10. Interference light having a plurality of peaks separated from each other at equal frequency intervals generated by interfering the emitted light L1 incident on the etalon 10 inside the etalon 10 is emitted into the atmosphere as the emitted light L2.

The light source 20 is, for example, a semiconductor laser element that emits pulsed laser light as emitted light L1. The beam mode of the emitted light L1 is, for example, a multi-mode, but may be a single mode. As an example, the light source 20 emits a laser beam having a peak in the vicinity of 405 nm as an emitted light L1. Alternatively, the light source 20 may be a light emitting diode (LED: Light Emitting Diode). Further, the light source 20 may be a discharge lamp such as a halogen lamp.

The mirror 22 reflects the emitted light L1. By arranging the mirror 22 at an appropriate angle with respect to the emitted light L1, the course of the emitted light L1 can be bent in a desired direction. In the present embodiment, the mirror 22 reflects the emitted light L1 and causes it to enter the etalon 10. The aerosol measuring device 1 does not have to include the mirror 22.

The light collecting unit 30 is a member that collects the scattered light L3 generated by the scattering body 90 contained in the atmosphere scattering the emitted light L2. The light collecting unit 30 is arranged between the scatterer 90 and the etalon 15. As an example of the condensing unit 30, there is, for example, the convex condensing lens 30a shown in FIG. 1, or at least one reflecting mirror. For example, the light collected by the condenser lens 30a is converted into parallel light and emitted by a lens group including a collimating lens. Therefore, the scattered light L3 collected by the condenser lens 30a is incident on the etalon 15. Further, the condensing unit 30 includes an optical element such as a collimating lens or a pinhole. When the signal intensity of the scattered light L3 is strong, the light collecting unit 30 may not be arranged. That is, the aerosol measuring device 1 does not have to include the condensing unit 30.

The condenser lens 40 collects the Mie scattered light L4 that has passed through the etalon 15 among the scattered light L3 condensed by the condenser lens 30a. The condenser lens 40 is, for example, a convex lens. The condenser lens 40 concentrates the Mie scattered light L4 on the light receiving surface of the receiver 50.

The light receiver 50 receives the Mie scattered light L4 that has passed through the etalon 15 among the scattered light L3 collected by the condenser lens 30a, and outputs a signal according to the light receiving intensity. The light receiving intensity is the intensity of the Mie scattered light L4, and is represented by, for example, the signal level of the signal output by the light receiver 50.

The light receiver 50 is an element that performs photoelectric conversion, for example, a PMT (Photomultiplier Tube). Alternatively, the receiver 50 may have a PMT and a photon counter. Further, the receiver 50 may be an avalanche photodiode.

The analysis unit 60 analyzes the aerosol contained in the scatterer 90 by analyzing the signal output from the receiver 50. For example, the analysis unit 60 determines the presence / absence and concentration of aerosol based on the signal level of the signal. Specifically, the analysis unit 60 determines the concentration of the aerosol corresponding to the signal level by referring to the correspondence information in which the signal level and the concentration of the aerosol are associated with each other. Correspondence information is stored in advance in, for example, a memory (not shown) included in the analysis unit 60.

Further, the analysis unit 60 calculates the distance to the aerosol by the TOF (Time Of Flight) method based on the time required from the emission of the emitted light L2 to the reception of the Mie scattered light L4. The analysis unit 60 identifies the position of the aerosol in the target space based on the calculated distance and the direction in which the emitted light L2 is emitted. By repeating the identification of the position of the aerosol while changing the emission direction of the emitted light L2, the analysis unit 60 creates the distribution of the aerosol in the target space.

The analysis unit 60 is composed of one or a plurality of electronic circuits including a plurality of circuit components. Each of the one or more electronic circuits may be a general-purpose circuit or a dedicated circuit. That is, the function executed by the analysis unit 60 is realized by hardware such as an electronic circuit. Alternatively, the analysis unit 60 may be realized by a non-volatile memory in which the program is stored, a volatile memory which is a temporary storage area for executing the program, an input / output port, a processor in which the program is executed, or the like. The function executed by the analysis unit 60 may be realized by software executed by the processor.

The control unit 70 changes at least one optical path length selected from the group consisting of the optical path length of the emitted light L1 in the etalon 10 and the optical path length of the scattered light L3 in the etalon 15. In the present embodiment, the control unit 70 changes the optical path length of the scattered light L3 in the etalon 15. Specifically, the control unit 70 changes the optical path length of the scattered light L3 in the etalon 15 by controlling the heater 80.

The control unit 70 is composed of one or a plurality of electronic circuits including a plurality of circuit components. Each of the one or more electronic circuits may be a general-purpose circuit or a dedicated circuit. That is, the function executed by the control unit 70 is realized by hardware such as an electronic circuit. The control unit 70 may be, for example, a microcontroller. Specifically, the control unit 70 is realized by a non-volatile memory in which the program is stored, a volatile memory which is a temporary storage area for executing the program, an input / output port, a processor for executing the program, and the like. May be good. The function executed by the control unit 70 may be realized by software executed by the processor. The control unit 70 and the analysis unit 60 may share hardware resources such as memory.

The heater 80 is an example of a temperature adjusting device that adjusts the temperature of at least one of the etalons 10 and 15. In this embodiment, the heater 80 adjusts the temperature of the etalon 15. The etalon 15 thermally expands or contracts as the temperature changes. As a result, the optical path length of the scattered light L3 passing through the etalon 15 changes. The purpose of changing the optical path length and the details of the specific processing will be described later.

Each component included in the aerosol measuring device 1 is housed inside a housing (not shown), for example. The housing is an outer housing of the aerosol measuring device 1 and has a light-shielding property. The housing is provided with an opening for passing the emitted light L2 and the scattered light L3. One aperture may be provided corresponding to each of the emitted light L2 and the scattered light L3. The condenser lens 30a may be provided in the aperture.

[2. motion]
Next, the operation of the aerosol measuring device 1 will be described with reference to FIG. FIG. 2 is a flowchart showing the operation of the aerosol measuring device 1 according to the present embodiment.

As shown in FIG. 2, first, the control unit 70 controls the heater 80 to adjust the optical path length (S10). Next, the light source 20 emits the emitted light L1 (S12). By passing through the etalon 10, the emitted light L1 is converted into multi-light, which is light having a plurality of peaks separated from each other at equal frequency intervals. That is, the etalon 10 internally interferes with the incident light and emits it as light having a plurality of peaks separated from each other at equal frequency intervals (S14). The emitted light L2, which is multi-light, is emitted into the atmosphere and scattered by the scatterer 90.

Next, the condenser lens 30a collects the scattered light L3 generated from the scatterer 90 (S16). The scattered light L3 collected by the condenser lens 30a passes through the etalon 15 to extract the Mie scattered light L4. That is, the scattered light collected by the condensing unit interferes with the inside of the etalon 15 and passes through the etalon 15. (S18). In other words, the etalon 15 substantially removes the Rayleigh scattered light among the scattered light L3 and allows only the Mie scattered light L4 to pass through.

Next, the light receiver 50 receives the Mie scattered light L4 and outputs a signal according to the light receiving intensity (S20).

The analysis unit 60 analyzes the aerosol contained in the scatterer 90 by analyzing the signal output from the receiver 50 (S22).

The aerosol measuring device 1 repeats the above processes from step S12 to step S22 while changing the emission direction of the emission light L2. For example, when the emitted light L2 is emitted in a predetermined direction in the target space and the scattered light L3 can be acquired, the position and concentration of the aerosol contained in the scattering body 90 that is the source of the scattered light L3 can be determined. Identify. As a result, the aerosol measuring device 1 can generate, for example, a distribution map showing the position and concentration of the aerosol in the target space. The aerosol measuring device 1 may generate a distribution map showing only the position of the aerosol.

Although FIG. 2 shows an example in which the optical path length is adjusted first, the optical path length may be adjusted repeatedly while measuring the aerosol. Specifically, as will be described later, the control unit 70 may periodically change the optical path length of the etalon 10 or 15 within a predetermined range. The emitted light L2 may be emitted and the Mie scattered light L4 may be received while periodically changing the optical path length.

[3. Function of Etalon]
Subsequently, the specific functions of the etalons 10 and 15 will be described.

As described above, the etalon 10 is a multi-laser light composed of light having a plurality of peaks separated from each other at equal frequency intervals by internally interfering with the emitted light L1 which is a laser light emitted from the light source 20. It is emitted as emitted light L2. In the following, first, the multi-laser light will be described with reference to FIG.

FIG. 3 is a diagram showing an example of the spectrum of the multi-laser light emitted by the aerosol measuring device 1 according to the present embodiment. In each of the parts (a) and (b) of FIG. 3, the horizontal axis represents the frequency and the vertical axis represents the signal strength.

Part (a) of FIG. 3 shows the spectrum of the emitted light L2, which is the multi-laser light after passing through the etalon 10. Each of the plurality of peaks included in the spectrum corresponds to the plurality of peaks included in the emitted light L2. The frequency intervals LW2 of the plurality of peaks are equal to each other, for example, 3 GHz. Here, an example in which the signal intensities of a plurality of peaks are equal to each other is shown, but they may be different from each other. The center wavelength λ of the emitted light L2 is, for example, 405 nm.

Part (b) of FIG. 3 is an enlarged view of part (a) of FIG. 3, and shows one peak of the spectrum, that is, only one light contained in the emitted light L2 in an enlarged manner. The full width at half maximum LW1 of one light is, for example, 360 MHz. LW1 is 1/20 or more and 1/5 or less of LW2, but may be 1/8 or more and 1/10 or less.

In the present embodiment, when the emitted light L1 passes through the etalon 10, it is interfered with in the etalon 10 and emitted as the emitted light L2. The etalon 10 utilizes the interference between the incident light and the light that is repeatedly reflected in the etalon 10. When the phase of the incident light and the phase of the light repeatedly reflected in the etalon 10 match, interference that strengthens the light occurs, and the light is enhanced and transmitted in the etalon 10. The multilayer film 13 of the etalon 10 can transmit or reflect light. The transmittance of the multilayer film 13 is, for example, 75%, but the transmittance is not limited to this.

Here, FIGS. 4 and 5 are diagrams for explaining the light passing through the etalon 10 of the aerosol measuring device 1 according to the present embodiment, respectively. Specifically, FIG. 4 schematically shows the 0th transmitted light and the 1st transmitted light. FIG. 5 schematically represents the 0th transmitted light and the 2nd transmitted light. The same applies to the light passing through the etalon 15.

Etalon 10 allows a part of the incident light to pass through as it is. As shown in FIGS. 4 and 5, the light transmitted as it is without being reflected by the multilayer films 12 and 13 of the etalon 10 is the 0th transmitted light.

As shown in FIG. 4, the first transmitted light is light that is reflected once by the multilayer film 12 after the incident light is reflected once by the multilayer film 13. Interference occurs when the phases of the 0th transmitted light and the 1st transmitted light match, and the light corresponding to the first interference fringe is emitted. Interfering fringes will be described later with reference to FIGS. 7 and 8.

As shown in FIG. 5, the second transmitted light is light in which the incident light is reflected twice by the multilayer film 13 and the multilayer film 12, respectively. Interference occurs when the phases of the 0th transmitted light and the 2nd transmitted light match, and the light corresponding to the second interference fringe is emitted.

If the phase of the incident light and the phase of the light that repeats reflection do not match, the light that is reflected on the light incident side and passes through the etalon 10 becomes weak. As a result, the transmitted light has a periodic spectrum. That is, the etalon 10 can emit the emitted light L2 having the same frequency interval LW2 when the emitted light L1 is incident.

Note that, in FIGS. 4 and 5, the path of the light is shown diagonally in order to make it easy to understand how the light is reflected, but the same applies when the light is incident on the etalon 10 from the front. Here, the case where the light is incident on the etalon 10 from the front, that is, the case where the incident angle of the light with respect to the etalon 10 is 0 ° will be described. The frequency characteristics of the transmittance of the etalon 10 when light is obliquely incident on the etalon 10 will be described later.

The length Δx of the etalon 10 for realizing the frequency interval LW2 is determined based on the following equation (1). The length Δx of the etalon 10 is the distance between the multilayer film 12 and the multilayer film 13, that is, the thickness of the translucent portion 11, as shown in FIGS. 4 and 5.

In the formula (1), n ₀ is the refractive index in vacuum, for example 1.0. n is the refractive index of the translucent portion 11 of the etalon 10, which is 1.47 in the case of quartz. c is the speed of light, which is 3 × 10 ⁸ m / s. When LW2 = 3 GHz, the length Δx of the etalon is 34 mm from the above formula (1). Further, the length Δx of the etalon 10 is limited to about 80 mm in manufacturing. Therefore, the lower limit of LW2 is about 1.3 GHz.

The optical path difference dx when Fabry-Perot interference is caused by Etalon 10 is expressed by the following equation (2).

For example, when Δx = 34 mm, the optical path difference dx is 100 mm.

Next, the scattered light L3 generated by the scattering body 90 scattering the emitted light L2 shown in FIG. 3 will be described with reference to FIG.

FIG. 6 is a diagram showing an example of the spectrum of scattered light L3 generated by scattering the multi-laser light emitted by the aerosol measuring device 1 according to the present embodiment. In each of the parts (a) and (b) of FIG. 6, the horizontal axis represents the frequency and the vertical axis represents the signal strength.

Part (a) of FIG. 6 shows the spectrum of scattered light L3. The scattered light L3, like the emitted light L2, is composed of light having a plurality of peaks separated from each other at a frequency interval MW2 equal to each other. Each of the plurality of peaks included in the spectrum corresponds to the plurality of peaks included in the emitted light L2. The frequency interval MW2 of the scattered light L3 is equal to the frequency interval LW2 of the emitted light L2. Here, an example in which the signal intensities of a plurality of peaks are equal to each other is shown, but they may be different from each other.

Part (b) of FIG. 6 is an enlarged view of part (a) of FIG. 6, and shows one peak of the spectrum, that is, only one light included in the scattered light L3 in an enlarged manner.

As described above, the scattered light L3 includes Mie scattered light and Rayleigh scattered light. The spectrum of Mie scattered light is substantially the same as the spectrum of emitted light L2 before scattering. On the other hand, the frequency width of Rayleigh scattered light is widened by the thermal motion of the molecules that make up the atmosphere. Also, the intensity of Rayleigh scattered light is usually lower than the intensity of Mie scattered light.

Therefore, as shown in the part (b) of FIG. 6, the spectrum of the scattered light L3 has a shape in which the base of the peak is widened as compared with the spectrum of the emitted light L2 shown in FIG. The high peak in the center corresponds to Mie scattered light, and the base part corresponds to Rayleigh scattered light. In the part (b) of FIG. 6, the signal intensity of Rayleigh scattered light by the molecules constituting the atmosphere and the signal intensity of Mie scattered light by the aerosol are set to 3: 1. The signal strength here is represented by the area of the peak. Further, the full width at half maximum MW1 of the peak representing the Mie scattered light is equal to the full width at half maximum LW1 of the emitted light L2.

It is known that the full width at half maximum RW of the foot portion representing the Rayleigh scattered light is about 3.4 GHz to 3.9 GHz according to a general actual measurement. As an example, the full width at half maximum RW of Rayleigh scattered light can be 3.6 GHz (Δλ = 1.9 pm).

Note that Δλ is calculated based on the following equation (3).

In the formula (3), Δf = RW. c is the speed of light, which is 3 × 10 ⁸ m / s. λ is the central wavelength, which is 405 nm here.

In the present embodiment, by passing the scattered light L3 through the etalon 15, light having a plurality of peaks appearing at a frequency interval of 3 GHz, that is, Me scattered light is transmitted, and light of another frequency component, that is, Rayleigh scattered light can be removed.

FIG. 7 is a diagram showing the calculation result of the interferogram when the scattered light including the Mie scattered light by the aerosol and the Rayleigh scattered light by the molecules constituting the atmosphere are interfered with by the Michelson interferometer. In FIG. 7, the horizontal axis represents the optical path difference dx that causes interference, and the vertical axis represents the intensity of the interference light. FIG. 8 is an enlarged view of the region VIII surrounded by the broken line in FIG. 7.

As shown in FIGS. 7 and 8, an interference fringe appears every time the optical path difference dx becomes an integral multiple of Δx. The interference fringe of dx = 0 is defined as the 0th interference fringe, and the interference fringe of dx = n × Δx is defined as the nth interference fringe. n is a natural number. FIG. 8 shows the 0th interference fringe, the 1st interference fringe, and the 2nd interference fringe. The first interference fringe is the light generated by the interference between the 0th transmitted light and the 1st transmitted light shown in FIG. The second interference fringe is the light generated by the interference between the 0th transmitted light and the second transmitted light shown in FIG.

In the receiver 50, the interference light including the 0th interference fringe to the nth interference fringe is received as Mie scattered light L4. In the present embodiment, by adjusting the length Δx of the etalon 15, it is possible to remove the interference fringes based on the Rayleigh scattered light caused by atmospheric scattering. A method for determining a length Δx suitable for removing Rayleigh scattered light will be described.

FIG. 9 is a diagram for explaining the dependence of the interference fringe by the Michelson interferometer on the frequency interval of the emitted light L2 when there is no scattering by the aerosol and only the atmospheric scattering is considered. In the parts (a) to (l) of FIG. 9, the horizontal axis represents dx and the vertical axis represents the signal strength. In the parts (a) to (l) of FIG. 9, the frequency intervals LW2 of the emitted light L2 are 2.4 GHz, 3.0 GHz, 3.6 GHz, 3.7 GHz, 3.8 GHz, 3.9 GHz, 4 GHz, 5 GHz, respectively. It shows the calculation result of the interferogram in the case of 6 GHz, 10 GHz, 15 GHz, and 30 GHz.

As shown in FIG. 9, as the frequency interval LW2 increases, the number of appearing interference fringes increases, and the signal strength of the appearing interference fringes increases. For example, when the frequency interval LW2 is 2.4 GHz, substantially only the 0th interference fringe appears, and the first or more interference fringes do not appear. In the frequency interval LW2 in the range of 3.0 GHz to 4 GHz, the 0th interference fringe and the 1st interference fringe appear, and the second and higher interference fringes do not appear. When the frequency interval LW2 is 5 GHz, a second interference fringe appears in addition to the 0th interference fringe and the first interference fringe. In FIG. 9, the range in which the first interference fringe and above appear is represented by a broken line frame.

The appearance of the second or higher interference fringes when only atmospheric scattering is taken into consideration means that interference is occurring only by Rayleigh scattered light. That is, it means that the Rayleigh scattered light is transmitted when the Rayleigh scattered light is incident on the etalon 15. If the frequency interval LW2 of the emitted light L2 is 3.9 GHz or less, the first interference fringe becomes small, so that the transmission of Rayleigh scattered light is suppressed.

That is, the magnitude of the first interference fringe when the frequency interval LW2 of the emitted light L2 is 3.9 GHz is 50% or less of the magnitude of the first interference fringe of the frequency interval LW2. Therefore, since the first interference fringe is small, it is possible to suppress the Rayleigh scattered light from passing through the etalon 15.

From the above, when the frequency interval LW2 of the emitted light L2 is 3.9 GHz or less, Rayleigh scattered light can be efficiently removed from the scattered light L3. When the frequency interval LW2 of the emitted light L2 is 3.9 GHz, the length Δx of the etalon 15 including the translucent portion 16 made of quartz is about 26 mm according to the equation (1). That is, by using the etalon 15 having a length Δx of 26 mm or more, Rayleigh scattered light can be efficiently removed, and the measurement accuracy of the aerosol can be improved.

[4. Adjustment of optical path length for the characteristic difference between two etalons]
As described above, the aerosol measuring device 1 according to the present embodiment includes two etalons 10 and 15. Therefore, the path of the emitted light L1 and the path of the scattered light L3 can be easily separated. In addition, it is possible to increase the degree of freedom in designing the arrangement of each element and the light path in the aerosol measuring device 1.

As the etalons 10 and 15, etalons having the same optical characteristics as each other are used. However, it is difficult to make the optical characteristics of the etalons 10 and 15 completely the same due to the variation in the production of the etalons. Specifically, the length of the etalon 10 and the length of the etalon 15 may be different. For example, the length of the etalon 10 and the length of the etalon 15 may differ by about 10 μm due to manufacturing variations. In this case, the frequency characteristics of the light passing through the etalon 10 and the frequency characteristics of the light passing through the etalon 15 do not match.

The transmittance of the etalon 10 or 15 and the frequency interval FSR (Free Spectral Range) of the light having a plurality of peaks that have passed through the etalon 10 or 15 are represented by the following equations (4) and (5). ..

In formula (4), R is the reflectance of the end face of Etalon 10 or 15. A is the loss due to Etalon 10 or 15. n is the refractive index of the translucent portion 11 or 16 of the etalon 10 or 15. Δx is the length of etalon 10 or 15. λ is the center frequency of the emitted light L1 or the scattered light L3 incident on the etalon 10 or 15. c is the speed of light, which is 3 × 10 ⁸ m / s. θ is the incident angle of the emitted light L1 or the scattered light L3 with respect to the etalon 10 or 15. φ is the incident angle of the emitted light L1 or the scattered light L3 with respect to the translucent portion 11 or 16 of the etalon 10 or 15. θ and φ have a relationship of sinθ = nsinφ. The frequency interval FSR is the same as the frequency interval LW2 shown in FIG. 3 or the frequency interval MW2 shown in FIG.

The reflectance R of etalon 10 or 15 is, for example, 70% or more and 95% or less, and as an example, 74%. At this time, the ratio of the frequency interval FSR to the full width at half maximum LW1 or MW1 of the peak, that is, FSR / LW1 or FSR / MW1 is about 10. When the reflectance R becomes large, the full width at half maximum LW1 or MW1 of the peak becomes small. Therefore, the total intensity of the light having a plurality of peaks, specifically, the emitted light L2 or the Mie scattered light L4 is reduced. Further, when the reflectance R becomes small, the half-value full width at half maximum LW1 or MW1 of the peak becomes large. Therefore, the separation ability of Rayleigh scattered light is lowered, and the detection accuracy of the aerosol is lowered.

Here, the difference in the frequency characteristics of the transmittance due to the difference in length Δx between the two etalons 10 and 15 will be described with reference to FIG.

FIG. 10 is a diagram showing the frequency characteristics of the transmittances of two etalons having different optical path lengths. Part (a) of FIG. 10 represents a case where the length Δx of the etalon is 34.01 mm. Part (b) of FIG. 10 represents a case where the length Δx of the etalon is 34 mm. As is clear from a comparison between the portion (a) and the portion (b) of FIG. 10, it can be seen that the positions of the peaks of the transmittance are significantly deviated. The frequency interval FSR is substantially the same.

In the aerosol measuring device 1 according to the present embodiment, the control unit 70 adjusts the optical path length of the etalon 10 or 15 to determine the position of the peak of the transmittance of the etalon 10 and the position of the peak of the transmittance of the etalon 15. Synchronize. As a result, the light receiving intensity of the Mie scattered light L4 is increased, so that the aerosol detection accuracy is improved. Note that tuning is to make the frequency position of the transmittance peak of Etalon 10 substantially equal to the frequency position of the transmittance peak of Etalon 15. Specifically, the control unit 70 adjusts the optical path length of the etalon 10 or 15, so that the optical path length of the etalon 10 and the optical path length of the etalon 15 are the same.

FIG. 11 is a diagram showing an example of a change in the optical path length in the etalon 15 by the aerosol measuring device 1 according to the present embodiment. Part (a) of FIG. 11 represents the etalon 15 before heating or after cooling. Part (b) of FIG. 11 represents the etalon 15 after heating or before cooling.

As shown in FIG. 11, the etalon 15 is mainly equipped with a heater 80 that partially or wholly contacts and covers the side surface of the translucent portion 16. The heater 80 is, for example, a sheet-shaped silicon rubber heater. The heater 80 may be a heating wire. The heater 80 is heated and stopped by the control unit 70, and the target temperature for heating and the rate of temperature rise are controlled.

A temperature sensor 71 is provided between the heater 80 and the etalon 15. The temperature sensor 71 is, for example, a thermistor or a thermocouple, but is not limited to this. The temperature sensor 71 measures the temperature of the etalon 15 and outputs the measurement result to the control unit 70. The control unit 70 controls the heater 80 based on the measurement result by the temperature sensor 71. The temperature sensor 71 measures, for example, the surface temperature of the etalon 15, but may also measure the temperature inside the etalon 15.

As shown in FIG. 11, when the heater 80 heats the etalon 15, the length Δx of the etalon 15 changes. For example, the portion (a) of FIG. 11 shows a case where the length Δx of the etalon 15 is Δx1. By heating the etalon 15, the translucent portion 16 formed of quartz is thermally expanded. As a result, as shown in the portion (b) of FIG. 11, the length Δx of the etalon 15 becomes Δx2, which is longer than Δx1. Therefore, the optical path length of the scattered light L3 incident on the etalon 15 becomes long.

On the other hand, when the etalon 15 is cooled, the translucent portion 16 contracts. As a result, the length Δx of the etalon 15 is shortened. In this way, the control unit 70 can heat or cool the etalon 15 and change the optical length of the etalon 15 by controlling the heater 80.

In the present embodiment, the control unit 70 periodically changes the optical path length of the scattered light L3 in the etalon 15 within a predetermined range. Specifically, the control unit 70 periodically changes the temperature of the etalon 15 within a predetermined range to periodically change the optical path length.

FIG. 12 is a diagram showing the relationship between the temperature difference of etalon and the intensity of emitted light. In FIG. 12, the horizontal axis represents the temperature difference between the etalon 10 and the etalon 15, and the vertical axis represents the intensity of the emitted light.

As shown in FIG. 12, the peak of the intensity of the emitted light appears in the range where the temperature difference is 5 ° C. or higher and 7 ° C. or lower. The intensity peak appears when the position of the peak of Etalon 10 and the position of the peak of Etalon 15 are synchronized. In the example shown in FIG. 12, the intensity of the emitted light is maximized when the temperature difference is about 5.8 ° C. For example, the control unit 70 periodically changes the temperature difference in the range of 5 ° C. or higher and 7 ° C. or lower. As a result, the optical path length in the etalon 15 also changes periodically. Since the timing at which the peak position of the etalon 10 and the peak position of the etalon 15 are synchronized is included in the range of the periodic change, the Mie scattered light L4 having sufficient intensity is received by the receiver 50.

Note that the difference between the optical path length of the Etalon 10 and the optical path length of the Etalon 15 can occur not only during manufacturing variations but also during operation. For example, since the etalon 10 is close to the light source 20, it is affected by the heat generated by the light source 20 and is more likely to be thermally expanded during operation than the etalon 15. According to the aerosol measuring device 1 according to the present embodiment, even if the length of the etalon 10 changes, the position of the peak of the etalon 10 and the position of the peak of the etalon 15 can be changed by changing the temperature of the etalon 15. Can be synchronized. Therefore, it is possible to suppress a decrease in detection accuracy due to operation variation.

(Embodiment 2)
Subsequently, the second embodiment will be described.

In the second embodiment, the means for changing the optical path length in the etalon 10 or 15 is different from that of the first embodiment. Specifically, in the second embodiment, the inclination of the optical axis of the etalon 10 or 15 is adjusted. In the following, the differences from the first embodiment will be mainly described, and the common points will be omitted or simplified.

FIG. 13 is a diagram showing the configuration of the aerosol measuring device 101 according to the present embodiment. As shown in FIG. 13, the aerosol measuring device 101 includes a control unit 170 and a shaft adjusting device 180 instead of the control unit 70 and the heater 80, as compared with the aerosol measuring device 1 according to the first embodiment. Is different.

The control unit 170 changes at least one optical path length selected from the group consisting of the optical path length of the emitted light L1 in the etalon 10 and the optical path length of the scattered light L3 in the etalon 15. In the present embodiment, the control unit 170 changes the optical path length of the scattered light L3 in the etalon. Specifically, the control unit 170 changes the optical path length of the scattered light L3 in the etalon 15 by controlling the axis adjusting device 180. The control unit 170 is, for example, a microcontroller.

The axis adjusting device 180 adjusts the inclination of at least one of the optical axes of the etalons 10 and 15. In the present embodiment, the axis adjusting device 180 adjusts the inclination of the optical axis of the etalon 15. By changing the inclination of the optical axis of the etalon 15, the optical path length of the scattered light L3 passing through the etalon 15 changes.

The shaft adjusting device 180 includes, for example, a support portion that supports the etalon 15 and a stepping motor that rotates the support portion. The stepping motor, for example, rotates the support portion in parallel with the optical axis of the etalon 15 and in a plane including the optical axis. As a result, the optical axis of the etalon 15 can be tilted. The shaft adjusting device 180 may include an actuator instead of the stepping motor, and is not particularly limited. Here, the optical axis of etalon means an axis perpendicular to the multilayer film surface of etalon.

FIG. 14 is a diagram showing an example of a change in the optical path length of the scattered light L3 in the etalon 15 by the aerosol measuring device 101 according to the present embodiment. Part (a) of FIG. 14 shows a case where the optical axis P of the etalon 15 coincides with the incident direction of the scattered light L3, that is, a case where the incident angle θ of the scattered light L3 is 0 °. Part (b) of FIG. 14 shows a case where the optical axis P of the etalon 15 is inclined at an angle α with respect to the incident direction of the scattered light L3, that is, a case where the incident angle θ of the scattered light L3 is α. ing.

As shown in FIG. 14, when the axis adjusting device 180 tilts the optical axis P of the etalon 15, the incident angle of the scattered light L3 incident on the etalon 15 changes. Since the traveling direction of the scattered light L3 changes due to the refraction due to the change in the incident angle, the distance through which the scattered light L3 passes through the light transmitting portion 16 changes. For example, in the part (a) of FIG. 14, scattered light L3 is incident on the etalon 15 from the front. When the axis adjusting device 180 tilts the optical axis P of the etalon 15, the optical path length of the scattered light L3 passing through the translucent portion 16 of the etalon 15 becomes long as shown in the portion (b) of FIG. In the part (b) of FIG. 14, the change in the traveling direction due to the refraction of the scattered light L3 at the interface between the translucent portion 16 and each of the multilayer films 17 and 18 is omitted.

On the other hand, by reducing the inclination of the optical axis P, the optical path length of the scattered light L3 in the etalon 15 becomes shorter. In this way, the control unit 170 can change the inclination of the optical axis P of the etalon 15 and change the optical path length of the scattered light L3 in the etalon 15 by controlling the axis adjusting device 180.

In the present embodiment, the control unit 170 periodically changes the optical path length of the scattered light L3 in the etalon 15 within a predetermined range. Specifically, the control unit 170 periodically changes the optical path length by periodically changing the inclination of the optical axis P of the etalon 15 within a predetermined range.

FIG. 15 is a diagram showing the relationship between the inclination of the optical axis P of the etalon 15 and the intensity of the emitted light. In FIG. 15, the horizontal axis represents the angle of inclination of the optical axis P of the etalon 15, and the vertical axis represents the intensity of the emitted light.

As shown in FIG. 15, the peak of the intensity of the emitted light appears in the range where the angle α of the optical axis P is 0.125 ° or more and 0.175 ° or less. In the example shown in FIG. 15, the intensity of the emitted light is maximized when the angle α of the optical axis P is about 0.144 °. For example, the control unit 170 periodically changes the angle α in the range of 0.125 ° or more and 0.175 ° or less. As a result, the optical path length of the scattered light L3 in the etalon 15 also changes periodically. Since the timing at which the peak position of the etalon 10 and the peak position of the etalon 15 are synchronized is included in the range of the periodic change, the Mie scattered light L4 having sufficient intensity is received by the receiver 50.

Note that the control unit 170 may adjust the temperature of the etalon 10 or 15 in the same manner as in the first embodiment, in addition to adjusting the inclination of the optical axis P of the etalon 10 or 15. That is, the aerosol measuring device 101 may include a heater 80.

(Embodiment 3)
Subsequently, the third embodiment will be described.

In the first and second embodiments, the incident surface of the emitted light L1 with respect to the etalon 10 and the incident surface of the scattered light L3 with respect to the etalon 15 are located on opposite sides of each other. On the other hand, in this modification, the incident surface of the emitted light L1 with respect to the etalon 10 and the incident surface of the scattered light L3 with respect to the etalon 15 are located on the same side. In the following, the differences from the first or second embodiment will be mainly described, and the common points will be omitted or simplified.

FIG. 16 is a diagram showing the configuration of the aerosol measuring device 201 according to the present embodiment. As shown in FIG. 16, the aerosol measuring device 201 includes mirrors 32, 34 and 36 instead of the mirror 22 as compared with the aerosol measuring device 1 shown in FIG. Further, the arrangement of the light source 20, the condenser lens 40, the receiver 50, and the analysis unit 60 is different from that of the first embodiment.

As shown in FIG. 16, the mirrors 32 and 34 reflect the scattered light L3 condensed by the condenser lens 30a. By arranging the mirrors 32 and 34 at an appropriate angle with respect to the scattered light L3, the course of the scattered light L3 can be bent in a desired direction. In the present embodiment, the mirrors 32 and 34 reflect the scattered light L3 and make it incident on the etalon 15.

The mirror 36 reflects the Mie scattered light L4 that has passed through the etalon 15. By arranging the mirror 36 at an appropriate angle with respect to the Mie scattered light L4, the course of the Mie scattered light L4 can be bent in a desired direction. In the present embodiment, the Mie scattered light L4 is reflected and incident on the receiver 50 via the condenser lens 40.

As a result, as shown in FIG. 16, the light source 20 and the receiver 50 can be arranged apart from each other. Specifically, of the emitted light L1 emitted from the light source 20, the reflected light reflected by the etalon 10 can be made difficult to enter the receiver 50. The reflected light causes false detection of aerosol. Further, since the reflected light has a higher intensity than the scattered light, the intensity exceeds the limit intensity that can be detected by the receiver 50 and may cause a failure of the receiver 50. Therefore, according to the present embodiment, it is possible to suppress erroneous detection of aerosol due to reflected light and failure of the receiver 50.

Further, in the present embodiment, the scattered light L3 reflected by the mirror 34 is obliquely incident on the etalon 15. The incident angle θ of the scattered light L3 is, for example, 5 ° or less. As a result, the optical path difference dx that causes Fabry-Perot interference when the scattered light L3 passes through the etalon 15 is represented by the following equation (6).

At this time, the amount of change Δdx from the case of θ = 0 is expressed by the equation (7).

By adjusting the amount of change Δdx of the optical path difference to be an integral multiple of the wavelength λ of the light emitted by the light source 20, it is possible to adjust to the bright point of interference due to the wavelength in the interference fringe.

(Embodiment 4)
Subsequently, the fourth embodiment will be described.

In the fourth embodiment, the receiver 50 has a function of blocking light incident on the predetermined period. In the following, the differences from the first, second, and third embodiments will be mainly described, and the common points will be omitted or simplified.

FIG. 17 is a diagram showing the configuration of the aerosol measuring device 301 according to the present embodiment. As shown in FIG. 17, the aerosol measuring device 301 is newly provided with a light-shielding portion 351 as compared with the aerosol measuring device 1 shown in FIG.

The light-shielding unit 351 blocks the emitted light L1 emitted by the light source 20. The light-shielding unit 351 is, for example, a movable light-shielding shutter. As shown by the white double-headed arrow in FIG. 17, the light-shielding portion 351 is movable between a position that covers the light-receiving surface of the receiver 50 and a position that does not cover the light-receiving surface. The position shown by the broken line in FIG. 17 is the position that covers the light receiving surface, and the light shielding portion 351 covers the light receiving surface, so that the light incident on the light receiving device 50 can be blocked. Further, when the light shielding portion 351 does not cover the light receiving surface, light can be incident on the light receiving receiver 50. The position of the light-shielding portion 351 is controlled by the receiver 50.

FIG. 18 is a diagram for explaining the operation of the light-shielding portion 351 of the aerosol measuring device 301 according to the present embodiment. In the part (a) of FIG. 18, the horizontal axis represents time and the vertical axis represents the intensity of the emitted light L1. In the part (b) of FIG. 18, the horizontal axis represents time and the vertical axis represents the light receiving intensity by the light receiver 50.

As shown in the part (a) of FIG. 18, the light source 20 emits the pulsed emitted light L1. The time width tp of the emitted light L1 is, for example, 10 nanoseconds. For example, the light source 20 periodically emits a pulsed emitted light L1 having a time width of tp. The emission interval of the emitted light L1, that is, the time interval of the pulse is not particularly limited, but is longer than, for example, the time required for the light to travel twice the maximum distance at which the aerosol can be detected.

When the emitted light L1 is incident on the etalon 10, as shown in FIG. 17, some of the light is reflected as reflected light L5 on the incident side without passing through the etalon 10. When the reflected light L5 at this time is received by the light receiver 50, a signal corresponding to the intensity of the reflected light L5 is output as shown in the portion (b) of FIG.

Since the distance between the etalon 10 and the receiver 50 is sufficiently shorter than the distance between the scatterer 90 and the receiver 50, the reflected light L5 by the etalon 10 receives the Mie scattered light L4 after the emitted light L1 is emitted. The light is received by the light receiver 50 within the period until the light is received.

Therefore, in the present embodiment, the receiver 50 blocks the light reception for a predetermined period tm after the emitted light L1 is emitted by controlling the light-shielding unit 351. The period tm is a period longer than the time width tp of the pulsed emitted light L1. For example, the period tm is 10.1 nanoseconds. The start time of the period tm is, for example, the same as the emission of the emitted light L1.

As described above, according to the aerosol measuring device 301 according to the present embodiment, it is possible to suppress erroneous detection of aerosol due to reflected light and failure due to saturation of the receiver 50.

In the present embodiment, an example of physically blocking the light incident on the receiver 50 has been described, but the present invention is not limited to this. For example, among the signals output from the receiver 50, the signal corresponding to the reflected light may be ignored by the analysis unit 60, that is, it may not be used for aerosol analysis. Alternatively, the receiver 50 does not have to output a signal during the period tm. That is, the aerosol measuring device 301 may block the light incident on the receiver 50 in a signal processing manner.

(Other embodiments)
Although the aerosol measuring device and the aerosol measuring method according to one or more embodiments have been described above based on the embodiments, the present disclosure is not limited to these embodiments. As long as the gist of the present disclosure is not deviated, various modifications that can be conceived by those skilled in the art are applied to the present embodiment, and a form constructed by combining components in different embodiments is also included in the scope of the present disclosure. Is done.

For example, in the above embodiment, the optical path length of the scattered light L3 in the etalon 15 has been described, but the optical path length of the emitted light L1 in the etalon 10 may be changed. The optical path length in each of the etalons 10 and 15 may be changed.

Specifically, as shown in the above embodiment, the optical path length of the scattered light L3 in the etalon may be changed in one direction while the optical path length of the emitted light L1 in the etalon 10 is fixed. May be changed. The one direction is either a direction of increasing the optical path length or a direction of decreasing the optical path length.

Alternatively, the optical path length of the scattered light L3 in the etalon 15 may be changed in one direction while the optical path length of the emitted light L1 in the etalon 10 may be changed in one direction, or may be changed periodically. In this case, the optical path length of the scattered light L3 in the etalon 15 may be fixed.

Further, the optical path length of the scattered light L3 in the etalon 15 may be changed in one direction while the optical path length of the emitted light L1 in the etalon 10 may be changed periodically, or may be changed periodically. In this case, the optical path length of the scattered light L3 in the etalon 15 may be fixed.

Further, for example, the aerosol measuring device 1 may include a pressure adjusting device for adjusting the pressure of the etalon 10 or 15. In this case, the control unit 70 controls the pressure adjusting device. For example, the pressure adjusting device can compress the translucent portion 11 or 16 of the etalon 10 or 15 by pressurizing the etalon 10 or 15, and shorten the length Δx. As a result, the optical path length of the emitted light L1 or the scattered light L3 passing through the etalon 10 or 15 is shortened. Further, for example, the pressure adjusting device can extend the translucent portion 11 or 16 of the etalon 10 or 15 by reducing the pressure with respect to the etalon 10 or 15, and increase the length Δx. As a result, the optical path length of the emitted light L1 or the scattered light L3 passing through the etalon 10 or 15 becomes long. When the light transmitting portion 11 or 16 is an air layer, the length Δx can be easily changed by adjusting the pressure, and the optical path length can be easily changed.

Further, in the above embodiment, another processing unit may execute the processing executed by the specific processing unit. Further, the order of the plurality of processes may be changed, or the plurality of processes may be executed in parallel. Further, the distribution of the components of the aerosol measuring device to a plurality of devices is an example. For example, the components of one device may be included in another device. Further, the aerosol measuring device may be realized as a single device.

For example, the processing described in the above embodiment may be realized by centralized processing using a single device or system, or may be realized by distributed processing using a plurality of devices. .. Further, the number of processors that execute the above program may be singular or plural. That is, centralized processing may be performed, or distributed processing may be performed.

Further, in the above embodiment, all or a part of the components such as the analysis unit and the control unit may be configured by dedicated hardware, or by executing a software program suitable for each component. It may be realized. Even if each component is realized by a program execution unit such as a CPU (Central Processing Unit) or a processor reading and executing a software program recorded on a recording medium such as an HDD (Hard Disk Drive) or a semiconductor memory. Good.

Further, a component such as an analysis unit may be composed of one or a plurality of electronic circuits. The one or more electronic circuits may be general-purpose circuits or dedicated circuits, respectively.

The one or more electronic circuits may include, for example, a semiconductor device, an IC (Integrated Circuit), an LSI (Large Scale Integration), or the like. The IC or LSI may be integrated on one chip or may be integrated on a plurality of chips. Here, it is called IC or LSI, but the name changes depending on the degree of integration, and it may be called system LSI, VLSI (Very Large Scale Integration), or ULSI (Ultra Large Scale Integration). Further, FPGA (Field Programmable Gate Array) programmed after manufacturing the LSI can also be used for the same purpose.

Further, the general or specific aspects of the present disclosure may be realized by a system, an apparatus, a method, an integrated circuit or a computer program. Alternatively, it may be realized by a computer-readable non-temporary recording medium such as an optical disk, HDD or semiconductor memory in which the computer program is stored. Further, it may be realized by any combination of a system, an apparatus, a method, an integrated circuit, a computer program and a recording medium.

Further, in each of the above embodiments, various changes, replacements, additions, omissions, etc. can be made within the scope of claims or the equivalent scope thereof.

The present disclosure can be used as an aerosol measuring device or the like capable of easily and accurately measuring an aerosol, and can be used, for example, for measuring harmful fine particles indoors and observing weather outdoors.

1, 101, 201, 301 Aerosol measuring device 10, 15 Etalon 11, 16 Translucent part 12, 13, 17, 18 Multilayer film 20 Light source 22, 32, 34, 36 Mirror 30 Condensing part 30a, 40 Condensing lens 50 Receiver 60 Analytical unit 70, 170 Control unit 71 Temperature sensor 80 Heater 90 Scatterer 180 Axis adjuster 351 Shading unit L1, L2 Emission light L3 Scattered light L4 Me scattered light L5 Reflected light

Claims (13)

1. An aerosol measuring device for measuring aerosols contained in the atmosphere.
   Light source and
   A first etalon through which the first light emitted from the light source passes, and
   A second etalon through which the second light scattered by the aerosol passes, and
   A control unit for changing at least one optical path length selected from the group consisting of the optical path length of the first light in the first etalon and the optical path length of the second light in the second etalon is provided. ,
   Aerosol measuring device.
2. The first etalon irradiates the aerosol with interference light having a plurality of peaks separated from each other at equal frequency intervals, which is generated by internally interfering the first light.
   The second etalon emits Mie scattered light by internally interfering with the second light.
   The aerosol measuring device according to claim 1.
3. Further comprising a receiver for receiving the Mie scattered light.
   The aerosol measuring device according to claim 2.
4. The control unit changes the optical path length of the second light in the second etalon.
   The aerosol measuring device according to any one of claims 1 to 3.
5. The control unit periodically changes the at least one optical path length within a predetermined range.
   The aerosol measuring device according to any one of claims 1 to 3.
6. The frequency interval is 3.9 GHz or less.
   The aerosol measuring device according to claim 2 or 3.
7. Further, a temperature adjusting device for adjusting at least one selected from the group consisting of the temperature of the first etalon and the temperature of the second etalon is provided.
   The control unit changes the at least one optical path length by controlling the temperature adjusting device.
   The aerosol measuring device according to any one of claims 1 to 6.
8. Further, an axis adjusting device for adjusting at least one selected from the group consisting of the inclination of the optical axis of the first etalon and the inclination of the optical axis of the second etalon is provided.
   The control unit changes the at least one optical path length by controlling the axis adjusting device.
   The aerosol measuring device according to any one of claims 1 to 7.
9. The first light is pulsed light.
   The receiver is
   After the pulsed light is emitted from the light source, the reception of the Mie scattered light is stopped until a predetermined period longer than the time width of the pulsed light ends.
   After the predetermined period is completed, the Mie scattered light is received.
   The aerosol measuring device according to claim 3.
10. The second light enters the second etalon from an oblique direction with respect to the optical axis of the second etalon.
    The aerosol measuring device according to any one of claims 1 to 9.
11. The light source is a laser element or a light emitting diode.
    The aerosol measuring device according to any one of claims 1 to 10.
12. Further, it includes a condensing unit that condenses the second light and causes it to enter the second etalon.
    The aerosol measuring device according to any one of claims 1 to 11.
13. Making the first light emitted from the light source incident on the first etalon,
    Irradiating the aerosol contained in the atmosphere with the light emitted from the first etalon, and
    Injecting the second light scattered by the aerosol into the second etalon,
    An aerosol comprising varying at least one optical path length selected from the group consisting of the optical path length of the first light in the first etalon and the optical path length of the second light in the second etalon. Measurement method.

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