CN113125368B - Aerosol extinction instrument and measuring method thereof - Google Patents
Aerosol extinction instrument and measuring method thereof Download PDFInfo
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Abstract
The invention relates to an aerosol extinction instrument and a measuring method thereof, wherein the aerosol extinction instrument comprises: the device comprises a first light beam output module, a first light beam receiving module, a second light beam output module, a second light beam receiving module and a butterfly ring-down cavity; four inclined cavity mirrors are arranged in the butterfly ring-down cavity; the first light beam output module is used for outputting light beams with a first wavelength and outputting the light beams to the first cavity mirror; the second light beam output module is used for outputting light beams with a second wavelength and outputting the light beams to the third cavity mirror; the included angle between the direction of the light beam with the first wavelength and the direction of the light beam output to the first cavity mirror is not equal to 180 degrees, and the included angle between the direction of the light beam with the second wavelength and the direction of the light beam output to the third cavity mirror is not equal to 180 degrees. According to the scheme, measurement of aerosol extinction coefficients aiming at two wavelengths can be achieved at the same time under the condition that interference of optical feedback effect is reduced.
Description
Technical Field
The invention relates to the technical field of optical instruments, in particular to an aerosol extinction instrument and a measuring method thereof.
Background
An aerosol extinction instrument is an instrument for measuring the extinction coefficient of an aerosol. Wherein an aerosol is a homogeneous and relatively stable mixture of liquid or solid particles that may be suspended in air. Aerosols have an absorbing and scattering effect on the light propagating therein, both of which act in combination as extinction features. The extinction coefficient is typically used to characterize such extinction characteristics of an aerosol.
The cavity ring-down spectroscopy technology is used as an absorption spectroscopy technology with high sensitivity and high precision, and can be used for measuring the extinction coefficient of aerosol. In the related art, a cavity ring down technology-based aerosol extinction device generally employs a linear ring down cavity. But a linear ring down cavity can only measure the aerosol extinction coefficient for a single wavelength and is subject to interference from optical feedback effects.
In view of the above, there is a need to provide a new aerosol matting apparatus to address the above-mentioned deficiencies.
Disclosure of Invention
The invention aims to solve the technical problem of simultaneously measuring aerosol extinction coefficients for a plurality of wavelengths in a state of reducing interference of an optical feedback effect, and provides an aerosol extinction instrument and a measuring method thereof aiming at the defects in the prior art.
In order to solve the technical problems, the present invention provides an aerosol extinction apparatus, comprising: the device comprises a first light beam output module, a first light beam receiving module, a second light beam output module, a second light beam receiving module and a butterfly ring-down cavity;
the butterfly ring-down cavity is internally provided with a first inclined cavity mirror, a second inclined cavity mirror, a third inclined cavity mirror and a fourth inclined cavity mirror; the first light beam output module is used for outputting light beams with a first wavelength and outputting the light beams to the first cavity mirror; the second light beam output module is used for outputting light beams with a second wavelength and outputting the light beams to the third cavity mirror;
the first cavity mirror, the second cavity mirror, the third cavity mirror and the fourth cavity mirror are sequentially connected to form a quadrangle, and are used for transmitting the light beam with the first wavelength to the first light beam receiving module, reflecting the light beam with the first wavelength to the first cavity mirror, and enabling an included angle between the direction of the light beam with the first wavelength when reflecting to the first cavity mirror and the direction of the light beam with the first wavelength when being output to the first cavity mirror by the first light beam output module to be different from 180 degrees; and the second light beam receiving module is used for transmitting the light beam with the second wavelength to be output to the second light beam receiving module, reflecting the light beam with the second wavelength to the third cavity mirror, and forming an included angle between the direction of the light beam with the second wavelength when being reflected to the third cavity mirror and the direction of the light beam output to the third cavity mirror by the second light beam output module, wherein the included angle is not equal to 180 degrees.
Preferably, the method comprises the steps of,
the first, second, third and fourth cavity mirrors form the light path sequence when reflecting the light beam with the first wavelength to the first cavity mirror: the first cavity mirror, the second cavity mirror, the fourth cavity mirror and the third cavity mirror to the first cavity mirror;
the first, second, third and fourth cavity mirrors form the light path sequence when reflecting the light beam with the second wavelength to the third cavity mirror: the third, fourth, second, first through third endoscopes.
Preferably, the method comprises the steps of,
when the second cavity mirror reflects the light beam with the second wavelength to the first cavity mirror, the light beam with the second wavelength can vertically penetrate into the first light beam output module through the first cavity mirror;
when the fourth cavity mirror reflects the light beam with the first wavelength to the third cavity mirror, the light beam with the first wavelength can vertically penetrate through the third cavity mirror to enter the second light beam output module.
Preferably, the first, second, third and fourth cavity mirrors are identical plano-concave reflecting mirrors;
Concave surfaces of the first cavity mirror, the second cavity mirror, the third cavity mirror and the fourth cavity mirror face the inside of the butterfly ring-down cavity; and the concave surfaces are plated with high-reflection films, and the reflectivity of the high-reflection films to the light beams with the first wavelength and the light beams with the second wavelength is not smaller than a set reflection value.
Preferably, the quadrangle is rectangular.
Preferably, the distance between the two cavity mirrors located on the shorter side of the rectangle is not greater than a set distance;
the distance between the two cavity mirrors positioned on the longer side length of the rectangle and the distance between the two cavity mirrors positioned on the shorter side length of the rectangle meet the ABCD matrix theory.
Preferably, the method comprises the steps of,
further comprises: the first optical filter is positioned between the second cavity mirror and the first light beam receiving module and used for preventing the light beam with the second wavelength from entering the first light beam receiving module;
and/or the number of the groups of groups,
further comprises: and the second optical filter is positioned between the fourth cavity mirror and the second light beam receiving module and is used for preventing the light beam with the first wavelength from entering the second light beam receiving module.
Preferably, the method comprises the steps of,
the distance between the first optical filter and the first light beam receiving module is not smaller than 2mm;
And/or the number of the groups of groups,
the distance between the second optical filter and the second light beam receiving module is not smaller than 2mm.
Preferably, the method further comprises: two three-way gas passage interfaces, wherein one three-way gas passage interface is used for inputting gas into the butterfly ring-down cavity, and the other three-way gas passage interface is used for outputting the gas in the butterfly ring-down cavity to the outside of the butterfly ring-down cavity;
the three-way air passage interface is of a Y-shaped structure, two vent holes of the three-way air passage interface extend into the butterfly ring-down cavity, and a third vent hole is positioned outside the butterfly ring-down cavity.
The embodiment of the invention also provides a method for measuring the extinction coefficient of the aerosol based on any one of the aerosol extinction instruments, which comprises the following steps:
when zero gas is introduced into the butterfly ring-down cavity, a first time length required by the light intensity of the light beam received by the first light beam receiving module when the light intensity of the light beam is attenuated from a first set threshold value to 1/e of the first set threshold value is obtained, and a second time length required by the light intensity of the light beam received by the second light beam receiving module when the light intensity of the light beam received by the second light beam receiving module is attenuated from a second set threshold value to 1/e of the second set threshold value is obtained;
When the aerosol is introduced into the butterfly ring-down cavity, a third time length required by the light intensity of the light beam received by the first light beam receiving module when the light intensity of the light beam is attenuated from a first set threshold value to 1/e of the first set threshold value is acquired, and a fourth time length required by the light intensity of the light beam received by the second light beam receiving module when the light intensity of the light beam received by the second light beam receiving module is attenuated from a second set threshold value to 1/e of the second set threshold value is acquired;
calculating an extinction coefficient of the aerosol when the light beam is of the first wavelength according to the first time length and the third time length;
and calculating the extinction coefficient of the aerosol when the light beam is at the second wavelength according to the second time length and the fourth time length.
The aerosol extinction instrument comprises two light beam output modules and two light beam receiving modules, wherein the two light beam output modules can emit light beams with different wavelengths, and the two light beam receiving modules can respectively receive the light beams with the two different wavelengths, so that aerosol extinction coefficient measurement can be performed on the two wavelengths at the same time. In addition, the inclined first cavity mirror, the inclined second cavity mirror, the inclined third cavity mirror and the inclined fourth cavity mirror are arranged in the butterfly ring-down cavity, and the first cavity mirror, the second cavity mirror, the inclined third cavity mirror and the inclined fourth cavity mirror are sequentially connected to form a quadrangle and are used for reflecting the light beam with the first wavelength to the first cavity mirror, and the included angle between the direction of the light beam with the first wavelength reflected to the first cavity mirror and the direction of the light beam with the first wavelength output to the first cavity mirror is not equal to 180 degrees, so that the reflected light beam with the first wavelength cannot vertically enter the first light beam output module or cannot enter the first light beam output module, and the interference of the light feedback effect on the first light beam output module can be reduced; similarly, the interference of the optical feedback effect on the second beam output module can be reduced. Therefore, the method can realize simultaneous measurement of aerosol extinction coefficients for two wavelengths in a state of reducing interference of optical feedback effect.
Drawings
FIG. 1 is a schematic diagram of an aerosol extinction device according to an embodiment of the invention;
FIG. 2 is a schematic diagram of another aerosol matting apparatus according to an embodiment of the present invention;
FIG. 3 is a flow chart of a method for measuring an aerosol extinction coefficient according to an embodiment of the invention;
FIG. 4 is a schematic diagram of a laser output laser beam according to an embodiment of the present invention;
FIG. 5 is a schematic diagram of a light intensity of a laser detected by a photodetector according to an embodiment of the present invention;
FIG. 6 is a schematic diagram of the intensity of laser light detected by another photodetector according to an embodiment of the invention;
FIG. 7 is a schematic diagram of another laser output laser beam according to an embodiment of the present invention;
FIG. 8 is a schematic view of the intensity of laser light detected by another photodetector according to an embodiment of the invention;
FIG. 9 is a schematic diagram of the intensity of laser light detected by another photodetector according to an embodiment of the invention;
the reference numerals are as follows:
1-a first laser; 2-a first beam shaping module; 3-a first endoscope; 4-a second endoscope; 5-a first filter; 6-a first lens; 7-a first photodetector; 8-a second photodetector; 9-a second lens; 10-a second filter; 11-fourth cavity mirror; 12-a third endoscope; 13-a second beam shaping module; 14-a second laser; a 15-A type sleeve; 16/18-three-way air passage interface; 17-a butterfly ring down chamber; 19-adjusting the frame; 20-a universal sleeve; a 21-B type sleeve; 22-a first beam output module; 23-a first beam receiving module; 24-a second beam output module; 25-a second beam receiving module.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
As before, in the related art, the cavity ring-down technology-based aerosol extinction device includes a beam output module, a beam receiving module, and a linear ring-down cavity to measure an aerosol extinction coefficient for a single wavelength. The linear ring-down cavity consists of two cavity mirrors (such as a cavity mirror A and a cavity mirror B), and the two cavity mirrors are vertically arranged. The light beam output by the light beam output module enters the linear ring-down cavity after passing through the cavity mirror A, and then the light beam passes through the cavity mirror B to the light beam receiving module. When the light beam enters the ring-down cavity, an optical feedback effect occurs, and the optical feedback effect is that: one part of the light beam entering the cavity mirror passes through the cavity mirror, and the other part of the light beam is reflected by the cavity mirror. When the light beam transmitted through the cavity mirror A reaches the cavity mirror B, the cavity mirror B transmits and outputs part of the light beam to the light beam receiving module and reflects the other part of the light beam. Because two chambered mirrors all set up perpendicularly, then chamber mirror B can be with the light beam perpendicular reflection to chamber mirror A on, the light beam that reflects to chamber mirror A can perpendicular incidence in the light beam output module through chamber mirror A to the light beam that launches to the light beam output module causes the interference.
Based on the above-mentioned problems, it is considered that when the optical feedback effect occurs in the ring-down cavity, the reflected light beam makes an angle when reaching the cavity mirror corresponding to the light beam output module, so as to prevent the reflected light beam from perpendicularly entering the light beam output module after penetrating through the cavity mirror corresponding to the light beam output module. As such, it is considered to set the endoscope obliquely to solve the above-described problem.
The specific idea of the present solution is described below.
As shown in fig. 1, an aerosol extinction apparatus according to an embodiment of the present invention includes: a first beam output module 22, a first beam receiving module 23, a second beam output module 24, a second beam receiving module 25, and a butterfly ring down cavity 17;
the first cavity mirror 3, the second cavity mirror 4, the third cavity mirror 12 and the fourth cavity mirror 11 which are inclined are arranged in the butterfly ring-down cavity 17; the first beam output module 22 is configured to output a beam of a first wavelength and output the beam to the first cavity mirror 3; the second beam output module 24 is configured to output a beam of a second wavelength and output the beam to the third cavity mirror 12;
the first cavity mirror 3, the second cavity mirror 4, the third cavity mirror 12 and the fourth cavity mirror 11 are sequentially connected to form a quadrangle, so that a light beam with a first wavelength is transmitted to be output to the first light beam receiving module 23, the light beam with the first wavelength is reflected to the first cavity mirror 3, and an included angle between the direction of the light beam with the first wavelength when being reflected to the first cavity mirror 3 and the direction of the light beam output to the first cavity mirror 3 by the first light beam output module 22 is not equal to 180 degrees; and is configured to transmit the light beam with the second wavelength to output to the second light beam receiving module 25, reflect the light beam with the second wavelength to the third cavity mirror 12, and an included angle between a direction of the light beam with the second wavelength when the light beam with the second wavelength is reflected to the third cavity mirror and a direction of the light beam output from the second light beam output module 24 to the third cavity mirror 12 is not equal to 180 degrees.
In the embodiment of the invention, the aerosol extinction instrument comprises the two light beam output modules and the two light beam receiving modules, the two light beam output modules can emit light beams with different wavelengths, and the two light beam receiving modules respectively receive the light beams with the two different wavelengths, so that the aerosol extinction coefficient can be measured for the two wavelengths at the same time.
In the embodiment of the invention, the inclined first cavity mirror, the inclined second cavity mirror, the inclined third cavity mirror and the inclined fourth cavity mirror are arranged in the butterfly ring-down cavity, and the first cavity mirror, the second cavity mirror, the inclined third cavity mirror and the inclined fourth cavity mirror are sequentially connected to form a quadrangle and are used for reflecting the light beam with the first wavelength to the first cavity mirror, and the included angle between the direction of the light beam with the first wavelength and the direction of the light beam with the first wavelength, which is output by the first light beam output module, is not equal to 180 degrees, so that the reflected light beam with the first wavelength cannot vertically enter the first light beam output module or cannot enter the first light beam output module, and the interference of the light feedback effect on the first light beam output module can be reduced; similarly, the interference of the optical feedback effect on the second beam output module can be reduced.
In one embodiment of the present invention, in order to achieve the purpose (denoted as a first purpose) that the angle between the direction when the light beam of the first wavelength is reflected to the first cavity mirror 3 and the direction when the light beam of the first wavelength is output to the first cavity mirror 3 is not equal to 180 degrees (denoted as a second purpose), and the purpose (denoted as a second purpose) that the angle between the direction when the light beam of the second wavelength is reflected to the third cavity mirror 12 and the direction when the light beam of the second wavelength is output to the third cavity mirror 12 is not equal to 180 degrees (denoted as a second purpose), the setting positions and setting angles of the first cavity mirror 3, the second cavity mirror 4, the third cavity mirror 12 and the fourth cavity mirror 11 may satisfy the following two conditions at the same time:
condition 1: the first, second, third and fourth mirrors 3, 4, 12 and 11 may form the following optical path sequence when reflecting the light beam of the first wavelength to the first mirror 3: a first cavity mirror 3, a second cavity mirror 4, a fourth cavity mirror 11, a third cavity mirror 12 to the first cavity mirror 3; for the sequence of the light paths, please refer to the arrow direction of the solid line portion in the butterfly ring-down chamber 17 in fig. 1;
condition 2: the first, second, third and fourth mirrors 3, 4, 12 and 11 may form the following optical path sequence when reflecting the light beam of the second wavelength to the third mirror 12: a third lumen 12, a fourth lumen 11, a second lumen 4, a first lumen 3 to a third lumen 12; for this sequence, reference is made to the arrow direction of the dashed line portion of the butterfly ring-down chamber 17 in fig. 1.
Therefore, the light path sequence formed by the internal reflection of the butterfly ring-down cavity of the light beams with two wavelengths is a butterfly shape, and after the four cavity mirrors are arranged in the butterfly ring-down cavity, the light path sequence of the light beams when the light beams are reflected in the butterfly ring-down cavity can be accurately obtained, so that the interference caused by the measurement process of the extinction coefficient of the aerosol due to the fact that the light path of the light beams in the butterfly ring-down cavity cannot be accurately obtained can be reduced.
In the embodiment of the present invention, the setting positions and setting angles of the four mirrors may be implemented by other setting manners besides implementing the first object and the second object by satisfying the above condition 1 and condition 2, and the reflection light path of the light beam with the first wavelength is taken as an example, and the reflection light path of the light beam with the second wavelength is the same as the reflection light path of the light beam with the first wavelength. For example, the light path sequence formed when the light beam with the first wavelength is reflected to the first cavity mirror 3 is as follows: the first cavity mirror 3, the second cavity mirror 4 and the third cavity mirror 12 to the first cavity mirror 3, or the first cavity mirror 3, the second cavity mirror 4 and the fourth cavity mirror 11 to the first cavity mirror 3.
In one embodiment of the present invention, the setting positions and setting angles of the first endoscope 3, the second endoscope 4, the third endoscope 12 and the fourth endoscope 11 may satisfy the following two conditions on the basis of satisfying the above condition 1 and condition 2:
Condition 3: when the second cavity mirror 4 reflects the light beam with the second wavelength to the first cavity mirror 3, the light beam with the second wavelength can vertically penetrate the first cavity mirror 3 and enter the first light beam output module 22;
condition 4: the fourth cavity mirror 11 reflects the light beam with the first wavelength to the third cavity mirror 12, and the light beam with the first wavelength can vertically penetrate the third cavity mirror 12 to enter the second light beam output module 24.
Since the light beam output by the first light beam output module 22 is of a first wavelength and different from the second wavelength, in general, for measurement of the extinction coefficient of the aerosol, the two wavelengths are not in the same wavelength band, so that the light beam of the second wavelength will not interfere with the first light beam output module when perpendicularly incident into the first light beam output module 22. Similarly, the light beam of the first wavelength does not interfere with the second output module when vertically incident into the second output module 24.
The first beam output module 22, the first cavity mirror 3, the second cavity mirror 4 and the first beam receiving module 23 are on the same straight line, then when the above condition 3 is satisfied, there may be: the first cavity mirror 3 can reflect the light beam with the first wavelength reflected by the third cavity mirror 12 to the second cavity mirror 4, and the light path of the first cavity mirror 3 for reflecting the light beam with the first wavelength to the second cavity mirror 4 is the same as the light path of the light beam with the first wavelength output by the first light beam output module for reaching the second cavity mirror 4 through the first cavity mirror 3, and the reflection light path of the light beam with the first wavelength in the butterfly ring-down cavity is a closed loop and the same light path, so that the influence caused by the optical feedback effect can be further reduced.
Similarly, the second beam output module 24, the third cavity mirror 12, the fourth cavity mirror 11, and the second beam receiving module 25 are on the same straight line, and then when the above condition 4 is satisfied, there may be: the third cavity mirror 12 can reflect the light beam with the second wavelength reflected by the first cavity mirror 3 to the fourth cavity mirror 11, and the light path of the light beam with the second wavelength reflected by the third cavity mirror 12 to the fourth cavity mirror 12 is the same as the light path of the light beam with the second wavelength output by the second light beam output module, which passes through the third cavity mirror 12 to reach the fourth cavity mirror 11, and the reflection light path of the light beam with the second wavelength in the butterfly ring-down cavity is a closed loop and the same light path, so that the influence caused by the optical feedback effect can be further reduced.
In one embodiment of the present invention, to ensure that the light beam is reflected inside the butterfly ring-down cavity, the first, second, third and fourth cavity mirrors may be the same plano-concave mirror; namely, one surface is a plane, and the other surface is a concave surface;
the concave surfaces of the first cavity mirror, the second cavity mirror, the third cavity mirror and the fourth cavity mirror face the inside of the butterfly ring-down cavity 17; and the concave surfaces are plated with high-reflection films, and the reflectivity of the high-reflection films to the light beams with the first wavelength and the light beams with the second wavelength is not smaller than a set reflection value.
For example, the first wavelength is 532nm and the second wavelength is 488nm, so that the high reflection film needs to ensure that the reflectivity of the light beams with the two wavelengths is not smaller than a set reflection value, for example, the set reflection value is 0.9999, so that the high reflection of the light beams with the two wavelengths can be realized by any cavity mirror.
Preferably, the planar surface may be coated with an anti-reflection film.
In one embodiment of the present invention, the first, second, third and fourth endoscopes may be identical or different, such as different radii of curvature, sizes, etc. The conditions of the present embodiment need to be satisfied when four mirrors are set, regardless of whether the four mirrors are identical, and design according to ABCD matrix theory (laser principle optical resonator theory in an optical system) is required.
Preferably, the quadrangle formed by sequentially connecting the four cavity mirrors can be rectangular, so that the volume of the aerosol extinction device can be ensured to be minimum during installation.
In one embodiment of the present invention, when four endoscopes are sequentially connected to form a rectangle, the defining of the side length may at least include:
the distance between the two cavity mirrors positioned on the shorter side length of the rectangle is not more than a set distance;
The distance between the two mirrors located on the longer side of the rectangle and the distance between the two mirrors located on the shorter side of the rectangle satisfy the ABCD matrix theory.
For example, the smaller the distance, the better the first and fourth mirrors 3 and 11 located on the shorter side of the rectangle in fig. 1, the smaller the volume of the aerosol extinction formed by the smaller distance, but the distance needs to ensure that the first and fourth mirrors 3 and 11 are not blocked and disturbed when being used for fine adjustment, and therefore, the set distance needs to be determined according to the model size of the mirrors, etc.
After the shorter side length is determined, the distance between the two cavity mirrors on the longer side length of the rectangle can be calculated according to the ABCD matrix theory, wherein the shorter side length and the longer side length satisfy the ABCD matrix theory.
In one embodiment of the present invention, referring to fig. 1, the aerosol extinction apparatus may further include:
a first filter 5, located between the second cavity mirror 4 and the first light beam receiving module 23, for preventing the light beam with the second wavelength from entering the first light beam receiving module 23;
and/or the number of the groups of groups,
the second filter 10 is located between the fourth cavity mirror 11 and the second light beam receiving module 25, and is used for preventing the light beam with the first wavelength from entering the second light beam receiving module 25.
For example, the first filter 5 may be a 532nm narrow band filter, which may prevent 488nm light from entering the first light beam receiving module, and the second filter 10 may be a 488nm narrow band filter, which may prevent 532nm light from entering the second light beam receiving module. Therefore, the influence on the light intensity received by the light beam receiving module can be reduced by adding the optical filter, so that the accuracy of a measurement result in aerosol measurement is improved.
In one embodiment of the present invention, the distance between the first optical filter 5 and the first light beam receiving module 23 is not less than 2mm;
and/or the number of the groups of groups,
the distance between the second filter 10 and the second light beam receiving module 25 is not less than 2mm.
If the distance is less than 2mm, the installation of the optical filter and the light beam receiving module is affected, so that the installation of each device can be facilitated and the production efficiency is improved by setting the distance between the optical filter and the light beam receiving module to be not less than 2mm when a product is formed.
Because zero gas or an aerosol sample needs to be introduced into the butterfly ring-down cavity when the aerosol extinction coefficient is measured by using the aerosol extinction instrument, two vent holes are also needed to be formed in the butterfly ring-down cavity, one vent hole is used for introducing gas into the butterfly ring-down cavity, and the other vent hole is used for discharging the gas in the butterfly ring-down cavity so as to ensure that the internal pressure and the external pressure of the ring-down cavity are the same.
In one embodiment of the present invention, the vent hole may be implemented by a three-way gas path interface, please refer to fig. 2, in which one three-way gas path interface 16 is used for inputting gas into the butterfly ring-down cavity, and the other three-way gas path interface 18 is used for outputting gas in the butterfly ring-down cavity to the outside of the butterfly ring-down cavity;
the three-way air passage interface is of a Y-shaped structure, two vent holes of the three-way air passage interface extend into the butterfly ring-down cavity, and the third vent hole is positioned outside the butterfly ring-down cavity.
Further, the two three-way gas circuit interfaces are positioned at two ends of the butterfly ring-down cavity, and the distance between the two vent holes extending into the butterfly ring-down cavity can be increased as much as possible, for example, the four vent holes extending into the butterfly ring-down cavity on the two three-way gas circuit interfaces are respectively positioned at four corners of the butterfly ring-down cavity, so that the distribution of the introduced gas in the butterfly ring-down cavity is more uniform, and the accuracy of the measurement result is improved.
In one embodiment of the present invention, the first beam output module and the second beam output module may each include a laser and a beam shaping module, where the laser is configured to output a laser beam with a corresponding wavelength, and the beam shaping module is configured to collimate the laser beam and perform mode matching with the butterfly ring-down cavity to achieve optimal coupling between the laser beam and the butterfly ring-down cavity.
The first light beam receiving module and the second light beam receiving module can both comprise a focusing lens and a photoelectric detector, wherein the focusing lens is used for focusing the light beam on the image surface of the photoelectric detector, namely, the distance between the focusing lens and the image surface of the photoelectric detector is equal to the focal length of the focusing lens, so that the photoelectric detector can detect the optimal light intensity of the light beam.
The preferred structure of the aerosol extinction device according to the embodiment of the present invention will be described below with reference to fig. 1 and 2, taking 532nm as a first wavelength and 488nm as a second wavelength.
The aerosol extinction device comprises a first beam output module 22 consisting of a first laser 1 and a first beam shaping module 2, a second beam output module 24 consisting of a second laser 14 and a second beam shaping module 13, a butterfly ring-down cavity 17 consisting of a first cavity mirror 3, a second cavity mirror 4, a fourth cavity mirror 11 and a third cavity mirror 12, two first optical filters 5 and second optical filters 10 corresponding to laser wavelengths, a first beam receiving module 23 consisting of a first lens 6 and a first photodetector 7, and a second beam receiving module 25 consisting of a second lens 9 and a second photodetector 8.
The first laser 1 adopts a continuous solid-state laser, the output wavelength is 532nm, the single-mode output is realized, and the beam quality M 2 <1.1。
The second laser 14 is a continuous semiconductor laser with an output wavelength of 488nm, single-mode output, and beam quality M 2 <1.1。
The first beam shaping module 2 has the function of collimating 532nm laser light emitted by the first laser 1 and performing mode matching with the butterfly ring-down cavity 17, so as to realize optimal coupling of the laser beam and the optical resonant cavity. The first beam shaping module 2 can be composed of three lenses, wherein 532nm antireflection films are plated on the surfaces of the lenses, and the substrate is fused quartz or K9 glass.
The function of the second beam shaping module 13 is to collimate the 488nm laser light emitted by the second laser 14 and to mode-match the butterfly ring-down cavity 17, so as to achieve optimal coupling of the laser beam with the optical resonator. The second beam shaping module 13 may be composed of three lenses, the surface of each lens is coated with 488nm antireflection film, and the substrate is fused silica or K9 glass.
The first laser 1 is connected to the first beam shaping module 2 by an a-type sleeve 15 and the second laser 14 is connected to the second beam shaping module 13 by a B-type sleeve 21. The A-type sleeve 15 and the B-type sleeve 21 are connected with a laser through external threads, and are connected with a beam shaping module through internal threads. The materials of the A-type sleeve 15, the B-type sleeve 21 and the general sleeve are aluminum 2A12, and the inner surface and the outer surface are blackened to inhibit specular reflection.
The butterfly ring-down cavity 17 is a ring-shaped optical resonant cavity and consists of four cavity mirrors (a first cavity mirror 3, a second cavity mirror 4, a third cavity mirror 11 and a fourth cavity mirror 12), and is made of stainless steel or microcrystalline glass. When the four cavity mirrors are identical, the four cavity mirrors can be flat concave reflecting mirrors, the concave surfaces are plated with high reflection films, the reflectivities at 532nm and 488nm are better than 0.9999, the plane is plated with an antireflection film, the four cavity mirrors are fixed in the butterfly ring-down cavity 17 through the stainless steel adjusting mirror frame 19, and the concave surfaces face the inside of the butterfly ring-down cavity.
For 532nm laser light emitted by the first laser 1, the order of the optical paths in the butterfly ring down cavity 17 is: the first cavity mirror 3, the second cavity mirror 4, the fourth cavity mirror 11 and the third cavity mirror 12 are connected with the first cavity mirror 3 to form a closed loop.
For 488nm laser light emitted by the second laser 14, the order of the optical paths in the butterfly ring down cavity 17 is: the third cavity mirror 12, the fourth cavity mirror 11, the second cavity mirror 4 and the first cavity mirror 3 to the third cavity mirror 12 form a closed loop opposite to the optical path of the first cavity mirror.
The first filter 5 is a 532nm narrow band filter for blocking 488nm laser beams from entering the first photodetector 7.
The second filter 10 is a 488nm narrowband filter for blocking 532nm laser light beams from entering the second photodetector 8.
The first lens 6 and the second lens 9 are short Jiao Pingtu lenses, the same type of lens can be selected, the material is K9 glass, and MgF2 antireflection films are plated on the surfaces of the first lens and the second lens.
The first photoelectric detector 7 and the second photoelectric detector 8 are gain-adjustable high-sensitivity detectors, and the same type of detectors can be selected.
The interval between the first optical filter 5 and the first lens 6 is more than or equal to 2mm, the plane of the first lens 6 faces the first optical filter 5, the convex surface faces the first photoelectric detector 7, and the distance from the plane of the first lens 6 to the image surface of the first photoelectric detector 7 is the focal length of the first lens 6. The first optical filter 5 and the first lens 6 are connected with the first photoelectric detector 7 through a universal sleeve 20, the first optical filter 5 and the first lens 6 are screwed into the internal thread of the universal sleeve 20 through the external thread on the lens frame, and the internal thread at one end of the universal sleeve 20 is connected with the external thread on the first photoelectric detector 7. The second filter 10, the second lens 9 and the second photodetector 8 are also connected as described above.
On the butterfly ring-down chamber 17, a three-way gas passage interface 16 for intake and a three-way gas passage interface 18 for exhaust are installed. The three-way air passage interface 16 and the three-way air passage interface 18 are made of nylon plastic, and the outer diameter size can be 6mm (or 8 mm) so as to ensure that the air passage is normal. The three-way gas path interface 16 and the three-way gas path interface 18 are connected with the gas inlet/exhaust pipe in a quick inserting mode, and are connected with the butterfly ring-down cavity 17 in a flange fixing mode.
Referring to fig. 3, the embodiment of the present invention further provides a method for measuring an aerosol extinction coefficient based on any one of the aerosol extinction instruments in the above embodiment, including:
step 301: when zero gas is introduced into the butterfly ring-down cavity, a first time length required by the light intensity of the light beam received by the first light beam receiving module when the light intensity is attenuated from the first set threshold value to 1/e of the first set threshold value is obtained, and a second time length required by the light intensity of the light beam received by the second light beam receiving module when the light intensity is attenuated from the second set threshold value to 1/e of the second set threshold value is obtained.
Step 302: when aerosol is introduced into the butterfly ring-down cavity, a third time length required by the light intensity of the light beam received by the first light beam receiving module when the light intensity is attenuated from the first set threshold value to 1/e of the first set threshold value is obtained, and a fourth time length required by the light intensity of the light beam received by the second light beam receiving module when the light intensity is attenuated from the second set threshold value to 1/e of the second set threshold value is obtained.
For steps 301 and 302, the time when the light intensity of the light beam received by the first light beam receiving module is attenuated from the first set threshold may be the same as the time when the light intensity of the light beam received by the second light beam receiving module is attenuated from the second set threshold, so that accuracy of the measurement result may be improved.
Step 303: calculating an extinction coefficient of the aerosol when the light beam is of a first wavelength according to the first time length and the third time length; and calculating the extinction coefficient of the aerosol when the light beam is at the second wavelength according to the second time length and the fourth time length.
The method for measuring the extinction coefficient of an aerosol in the embodiment of the present invention will be further described below by taking the preferred structure of the aerosol extinction device as an example.
The first step: starting the power supply of the aerosol extinction instrument
Active devices such as the first laser 1, the second laser 14, the first photoelectric detector 7, the second photoelectric detector 8 and the like are powered on, and gain values on the first photoelectric detector 7 and the second photoelectric detector 8 are adjusted, for example, set to 20dB by adjusting the magnitude of input current. At this time, the laser output switches of the first laser 1 and the second laser 14 are temporarily turned off.
And a second step of: introducing zero gas
Dry clean air which is dehumidified and decontaminated is introduced from an air inlet port of the three-way air passage port 16, the air flow rate is controlled to be 5L/min through a mass flowmeter, the exhaust gas is treated through an exhaust system of an aerosol extinction instrument from an exhaust port of the three-way air passage port 18, and the exhaust gas is released into the air at a far end under the harmless condition. The venting process requires about 30 seconds to wait for zero gas to be evenly distributed in the ring down chamber.
And a third step of: turning on a laser
The first laser 1 and the second laser 14 are started, and the light intensity of the laser transmitted from the second cavity mirror 4 and the fourth cavity mirror 11 respectively, which are received by the first photoelectric detector 7 and the second photoelectric detector 8, can be seen to rise rapidly through the data processing display and control device.
In the zero gas filling process, the laser beams output by the first laser 1 and the second laser 14 are shown in fig. 4.
In the zero gas filling process, the light intensities of the laser beams detected by the first photodetector 7 and the second photodetector 8 respectively refer to fig. 5 and 6 respectively.
Fourth step: turning off the laser
At t 01 At the moment, the light intensity of the laser transmitted from the second cavity mirror 4 reaches a first set threshold value of the first photoelectric detector 7, and the driving current of the first laser 1 is turned off through feedback control, so that the output of the laser beam is stopped; at the same time t 01 At this time, the light intensity of the laser light transmitted from the fourth cavity mirror 11 reaches the second set threshold value of the photodetector 8, and the drive current of the second laser 14 is feedback-controlled to be turned off, so that the output of the laser beam is stopped. From t 01 At this time, the light intensities of the light beams received by the first photodetector 7 and the second photodetector 8 are each attenuated from the maximum value (the first photodetector 7 is set at the first threshold value and the second photodetector 8 is set at the second threshold value), and the light intensities are each attenuated to 1/e of the maximum value received by each of the light intensities at the time t 11 Time sum t 21 Time of day.
Fifth step: repeated measurement of zero gas
In the multiple measurement mode, when the transmitted light intensities received in the first photodetector 7 and the second photodetector 8 are zero, the first laser 1 and the second laser 14 are automatically turned on under the feedback control. Repeating the third step and the fourth step to obtain multiple groups of t 01 、t 11 And t 21 Time of day.
Sixth step: calculating cavity ring down time
In the single measurement mode, the cavity ring down times at the two wavelengths are (t) 11 - t 01 ) And (t) 21 - t 01 ) The method comprises the steps of carrying out a first treatment on the surface of the In the multiple measurement mode, the average cavity ring-down times at two wavelengths are multiple sets (t 11 - t 01 ) And (t) 21 - t 01 ) Average value of (2).
Seventh step: introducing an aerosol sample
Aerosol samples are introduced from an air inlet interface of the three-way air passage interface 16, the flow speed of the samples is controlled to be 5L/min through a mass flowmeter, the discharged samples are treated through an exhaust system of an aerosol extinction instrument from an exhaust interface of the three-way air passage interface 18, the samples are released into the air at a far end under the harmless condition, and the samples are recovered and temporarily stored under the harmful condition. The aeration process requires about 30 seconds of waiting time and the sample can be uniformly distributed in the ring down chamber.
Eighth step: turning on a laser
The first laser 1 and the second laser 14 are turned on again, and the transmitted light intensity received by the first photodetector 7 and the second photodetector 8 rises rapidly.
Fig. 7 is a schematic diagram of laser beams output by the first laser 1 and the second laser 14 during the sample feeding process.
Please refer to fig. 8 and 9, which are schematic diagrams of the laser light intensities detected by the first photodetector 7 and the second photodetector 8 during the sample introduction process.
Ninth step: turning off the laser
At t 02 At the moment, the light intensity of the laser transmitted from the second cavity mirror 4 reaches a first set threshold value of the first photoelectric detector 7, and the driving current of the first laser 1 is turned off through feedback control, so that the output of the laser beam is stopped; at the same time t 02 At this time, the light intensity of the laser light transmitted from the fourth cavity mirror 11 reaches the second set threshold value of the photodetector 8, and the drive current of the second laser 14 is feedback-controlled to be turned off, so that the output of the laser beam is stopped. From t 02 At this time, the light intensities of the light beams received by the first photodetector 7 and the second photodetector 8 are each attenuated from the maximum value (the first photodetector 7 is set at the first threshold value and the second photodetector 8 is set at the second threshold value), and the light intensities are each attenuated to 1/e of the maximum value received by each of the light intensities at the time t 12 Time sum t 22 Time of day.
Tenth step: repeated measurement of aerosol samples
In the multiple measurement mode, when the transmitted light intensities received in the first photodetector 7 and the second photodetector 8 are zero, the first laser 1 and the second laser 14 are automatically turned on under the feedback control. Repeating the eighth step and the ninth step to obtain multiple groups of t 02 、t 12 And t 22 Time of day.
Eleventh step: calculating the ring down time of an aerosol sample
In the single-pass measurement mode,sample ring-down times at the two wavelengths were (t) 12 - t 02 ) And (t) 22 - t 02 ) The method comprises the steps of carrying out a first treatment on the surface of the In the multiple measurement mode, the average sample ring-down times at two wavelengths are multiple sets (t 12 - t 02 ) And (t) 22 - t 02 ) Average value of (2).
Twelfth step: calculation of the extinction coefficient of an aerosol
Extinction coefficient A of aerosol sample for first wavelength 1 Expressed as:
A 1 = [（t 12 - t 02 ） -1 -（t 11 - t 01 ） -1 ]·c -1
extinction coefficient A of aerosol sample for the second wavelength 2 Expressed as:
A 2 = [（t 22 - t 02 ） -1 -（t 21 - t 01 ） -1 ]·c -1
wherein c is the speed of light.
It will be appreciated that the structure illustrated in the examples of the present invention does not constitute a particular limitation of an aerosol matting apparatus. In other embodiments of the invention, the aerosol matting apparatus may comprise more or fewer components than shown, or certain components may be combined, or certain components may be split, or different arrangements of components. The illustrated components may be implemented in hardware, software, or a combination of software and hardware.
It is noted that relational terms such as first and second, and the like, are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the statement "comprises one" does not exclude that an additional identical element is present in a process, method, article or apparatus that comprises the element.
Those of ordinary skill in the art will appreciate that: all or part of the steps for implementing the above method embodiments may be implemented by hardware related to program instructions, and the foregoing program may be stored in a computer readable storage medium, where the program, when executed, performs steps including the above method embodiments; and the aforementioned storage medium includes: various media in which program code may be stored, such as ROM, RAM, magnetic or optical disks.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims (8)
1. An aerosol extinction instrument, comprising: the device comprises a first light beam output module, a first light beam receiving module, a second light beam output module, a second light beam receiving module and a butterfly ring-down cavity;
The butterfly ring-down cavity is internally provided with a first inclined cavity mirror, a second inclined cavity mirror, a third inclined cavity mirror and a fourth inclined cavity mirror; the first light beam output module is used for outputting light beams with a first wavelength and outputting the light beams to the first cavity mirror; the second light beam output module is used for outputting light beams with a second wavelength and outputting the light beams to the third cavity mirror;
the first cavity mirror, the second cavity mirror, the third cavity mirror and the fourth cavity mirror are sequentially connected to form a quadrangle, and are used for transmitting the light beam with the first wavelength to the first light beam receiving module, reflecting the light beam with the first wavelength to the first cavity mirror, and enabling an included angle between the direction of the light beam with the first wavelength when reflecting to the first cavity mirror and the direction of the light beam with the first wavelength when being output to the first cavity mirror by the first light beam output module to be different from 180 degrees; the second light beam receiving module is used for receiving the second light beam, reflecting the second light beam to the third cavity mirror, and enabling an included angle between the direction of the second light beam and the direction of the second light beam output to the third cavity mirror to be different from 180 degrees;
The first light beam output module, the first cavity mirror, the second cavity mirror and the first light beam receiving module are positioned on the same straight line; the second light beam output module, the third cavity mirror, the fourth cavity mirror and the second light beam receiving module are positioned on the same straight line;
the first, second, third and fourth cavity mirrors form the light path sequence when reflecting the light beam with the first wavelength to the first cavity mirror: the first cavity mirror, the second cavity mirror, the fourth cavity mirror and the third cavity mirror to the first cavity mirror;
the first, second, third and fourth cavity mirrors form the light path sequence when reflecting the light beam with the second wavelength to the third cavity mirror: the third, fourth, second, first to third endoscopes;
further comprises: the first optical filter is positioned between the second cavity mirror and the first light beam receiving module and used for preventing the light beam with the second wavelength from entering the first light beam receiving module;
and/or, further comprising: and the second optical filter is positioned between the fourth cavity mirror and the second light beam receiving module and is used for preventing the light beam with the first wavelength from entering the second light beam receiving module.
2. An aerosol matting apparatus as claimed in claim 1 in which,
when the second cavity mirror reflects the light beam with the second wavelength to the first cavity mirror, the light beam with the second wavelength can vertically penetrate into the first light beam output module through the first cavity mirror;
when the fourth cavity mirror reflects the light beam with the first wavelength to the third cavity mirror, the light beam with the first wavelength can vertically penetrate through the third cavity mirror to enter the second light beam output module.
3. The aerosol matting apparatus of claim 1 wherein the first, second, third and fourth mirrors are identical plano-concave mirrors;
concave surfaces of the first cavity mirror, the second cavity mirror, the third cavity mirror and the fourth cavity mirror face the inside of the butterfly ring-down cavity; and the concave surfaces are plated with high-reflection films, and the reflectivity of the high-reflection films to the light beams with the first wavelength and the light beams with the second wavelength is not smaller than a set reflection value.
4. An aerosol matting apparatus as claimed in claim 1, in which the quadrilateral is rectangular.
5. An aerosol matting apparatus according to claim 4 characterised in that the distance between the two mirrors on the shorter sides of the rectangle is no greater than a set distance;
The distance between the two cavity mirrors positioned on the longer side length of the rectangle and the distance between the two cavity mirrors positioned on the shorter side length of the rectangle meet the ABCD matrix theory.
6. An aerosol matting apparatus as claimed in claim 1 in which,
the distance between the first optical filter and the first light beam receiving module is not smaller than 2mm;
and/or the number of the groups of groups,
the distance between the second optical filter and the second light beam receiving module is not smaller than 2mm.
7. An aerosol matting apparatus as claimed in any one of claims 1 to 6, further comprising: two three-way gas passage interfaces, wherein one three-way gas passage interface is used for inputting gas into the butterfly ring-down cavity, and the other three-way gas passage interface is used for outputting the gas in the butterfly ring-down cavity to the outside of the butterfly ring-down cavity;
the three-way air passage interface is of a Y-shaped structure, two vent holes of the three-way air passage interface extend into the butterfly ring-down cavity, and a third vent hole is positioned outside the butterfly ring-down cavity.
8. A method of measuring an aerosol extinction coefficient based on an aerosol extinction instrument as claimed in any one of claims 1 to 7, comprising:
When zero gas is introduced into the butterfly ring-down cavity, a first time length required by the light intensity of the light beam received by the first light beam receiving module when the light intensity of the light beam is attenuated from a first set threshold value to 1/e of the first set threshold value is obtained, and a second time length required by the light intensity of the light beam received by the second light beam receiving module when the light intensity of the light beam received by the second light beam receiving module is attenuated from a second set threshold value to 1/e of the second set threshold value is obtained;
when the aerosol is introduced into the butterfly ring-down cavity, a third time length required by the light intensity of the light beam received by the first light beam receiving module when the light intensity of the light beam is attenuated from a first set threshold value to 1/e of the first set threshold value is acquired, and a fourth time length required by the light intensity of the light beam received by the second light beam receiving module when the light intensity of the light beam received by the second light beam receiving module is attenuated from a second set threshold value to 1/e of the second set threshold value is acquired;
calculating an extinction coefficient of the aerosol when the light beam is of the first wavelength according to the first time length and the third time length;
and calculating the extinction coefficient of the aerosol when the light beam is at the second wavelength according to the second time length and the fourth time length.
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| CN102116738B (en) * | 2010-11-30 | 2012-07-04 | 华中科技大学 | Methane gas sensing device based on fiber-loop ring-down cavity |
| CN103149156B (en) * | 2013-03-19 | 2015-10-07 | 中国气象科学研究院 | Binary channels optical cavity ring-down atmospheric aerosol delustring instrument and measurement of extinction coefficient method |
| CN103616334A (en) * | 2013-09-12 | 2014-03-05 | 复旦大学 | Cavity ring down aerosol extinction spectrometer |
| CN103674891B (en) * | 2013-12-02 | 2017-02-01 | 中国科学院安徽光学精密机械研究所 | Atmospheric NO3 free radical concentration measurement system based on double-cavity ring-down technology |
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| CN106483069A (en) * | 2015-08-26 | 2017-03-08 | 西安泰戈分析仪器有限责任公司 | Trace gas on-line analyses device based on cavity attenuation and vibration technique |
| CN105911020B (en) * | 2016-04-15 | 2018-11-30 | 中国科学院光电技术研究所 | Method for simultaneously measuring multi-component gas based on cavity ring-down spectroscopy |
| CN105651703B (en) * | 2016-04-19 | 2018-08-14 | 电子科技大学 | A kind of optical cavity ring-down gas measurement of extinction coefficient method changed based on chamber length |
| CN106841106B (en) * | 2016-12-12 | 2019-08-02 | 中国科学院光电研究院 | A kind of bi-component trace gas concentration measuring device based on Research on Cavity Ring Down Spectroscopy |
| WO2021007782A1 (en) * | 2019-07-16 | 2021-01-21 | 深圳先进技术研究院 | Cavity ring-down spectrometer system |
| CN110411718A (en) * | 2019-08-05 | 2019-11-05 | 中国科学院光电技术研究所 | Real-time measurement method of reflectivity and absorption of highly reflective components under continuous laser irradiation |
| CN110672554B (en) * | 2019-11-11 | 2020-09-25 | 北京航空航天大学 | Random vibration drive ring-down cavity calibration-free gas concentration measurement system |
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| CN112557327A (en) * | 2020-12-22 | 2021-03-26 | 天津城建大学 | New coronavirus COVID-19 marker detector and detection method |
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