JP2020134205A - Analyzer - Google Patents

Abstract

To reduce influence caused by different positions passing through an irradiation region of a laser beam for each particle.SOLUTION: An analyzer for analyzing particles on the basis of scattered light generated by scattering a laser beam with particles includes: a first detection section for detecting the scattered light; a second detection section in which a detection area for detecting that a spot image by the scattered light moves a predetermined distance on a light-receiving surface is provided; and a calculation section for calculating a distance of the particles passing through an irradiation region of the laser beam from a detection result by the first detection section and a detection result by the second detection section.SELECTED DRAWING: Figure 1

Description

The present invention relates to an analyzer.

An analyzer for particles contained in a gas is known. The analyzer detects one or both of the scattered light and the incandescent light generated when the particles pass through the irradiation region of the laser beam. The analyzer analyzes the number, size, mass concentration, etc. of particles based on the detection result (see, for example, Patent Document 1). For black carbon particles, the scattered light changes with time due to the sublimation of carbon and the shrinkage or disappearance of the particles as they pass through the irradiation region of the laser beam. Therefore, a technique for correcting a scattered light signal from information on a detection signal obtained by a divided detection element has been proposed (Non-Patent Document 1).

In order to improve the analysis accuracy, it is desirable that the particles pass through the center of the irradiation region of the laser beam. For example, in the apparatus shown in Patent Document 2, the particles are centered in the irradiation region of the laser beam by narrowing the flow path of the particles using guide air (sheath air) using a double nozzle structure and limiting the flow path. Pass near. However, there is a limit to the width of the particle flow path that can be narrowed down even if the double nozzle structure is used. The light intensity of the laser beam is not uniform in the irradiation region, and the center is higher than the periphery. Therefore, when the position where the particles pass through the laser beam irradiation region is different for each particle, the laser beam intensity experienced when the particles pass through the laser beam irradiation region is different for each particle. As a result, the measurement accuracy is affected.
[Prior art literature]
[Patent Document]
[Patent Document 1] Japanese Patent Application Laid-Open No. 2012-88178 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-189843 [Non-Patent Document]
[Non-Patent Document 1] Gao et al., Journal of Aerosol Science, 41: 2, pp. 125-135, 2007

It is desirable that the analyzer can reduce the influence of the position passing through the irradiation region of the laser beam being different for each particle.

In the first aspect of the present invention, an analyzer is provided. The analyzer may analyze the particles based on the scattered light generated by the particles scattering the laser light. The analyzer may include a first detection unit that detects scattered light. The analyzer may include a second detector. The second detection unit may be provided with a detection area. The detection region may detect that the spot image due to scattered light moves a predetermined distance on the light receiving surface. The analyzer may have a calculation unit. The calculation unit may calculate the distance that the particles have passed through the irradiation region of the laser beam from the detection result by the first detection unit and the detection result by the second detection unit.

The calculation unit may include a first calculation unit and a second calculation unit. The first calculation unit may calculate the time required for the particles to pass through the irradiation region of the laser beam from the detection result by the first detection unit. The second calculation unit may calculate the velocity of the particles from the detection result by the second detection unit. The calculation unit may calculate the distance that the particles have passed through the irradiation region of the laser beam from the time required for the particles to pass through the irradiation region and the velocity of the particles.

The detection region may be narrower in the traveling direction of the particles than the first detection unit.

The detection region may be a photoelectric conversion region that converts light into an electric signal. The detection region may be a dead zone sandwiched between two photoelectric conversion regions that convert light into an electric signal. The second detection unit may include a plurality of photoelectric conversion regions for converting light into an electric signal and a plurality of dead zones. A plurality of photoelectric conversion regions and a plurality of dead zones may be alternately arranged one by one. The plurality of dead zones may include a plurality of dead zones having different widths in the traveling direction of the particles. The detection region may be another photoelectric conversion region sandwiched between two photoelectric conversion regions that convert light into an electric signal.

The analyzer may include a difference calculation unit. The difference calculation unit may take the difference between the detection results in the two photoelectric conversion regions. The calculation unit may calculate the distance that the particles have passed through the irradiation region of the laser beam from the detection result by the first detection unit and the difference result.

The analyzer may further include a compensator. The correction unit may correct the analysis result of the particles based on the distance that the particles have passed through the irradiation region.

The correction unit may correct the detection result of the scattered light. The correction unit may correct the particle size of the particles calculated based on the scattered light. The correction unit may select particles that have passed through a predetermined region within the irradiation region of the laser beam based on the distance that the particles have passed through the irradiation region. The correction unit may correct the analysis result of the particles by selecting the particles.

The analyzer may further include an incandescent photodetector. The incandescent photodetector may detect the light emitted by the particles heated by the laser beam. The analyzer may further include a second correction unit. The second correction unit may correct the detection result by the incandescent light detection unit based on the distance that the particles have passed through the irradiation region.

The detection region may include a first detection region extending along the first direction and a second detection region extending along a second direction intersecting the first direction. The second calculation unit may calculate the first-direction component and the second-direction component of the particle velocity from the detection results in the first detection region and the second detection region in the second detection unit.

The outline of the above invention does not list all the necessary features of the present invention. Subcombinations of these feature groups can also be inventions.

It is a figure which shows the schematic structure of the analyzer 100 in one Embodiment of this invention. It is a figure which shows an example of the structure of the 1st detection part 30 and the 2nd detection part 40. It is a figure explaining an example of the 1st detection signal obtained by the 1st detection unit 30. It is a figure explaining an example of the 2nd detection signal obtained by the 2nd detection part 40. It is a figure which shows the method of calculating the velocity of a particle based on the 2nd detection signal. It is a figure which shows the method of calculating the laser passage distance from the velocity of a particle, and the passage time of a particle in an irradiation area. It is a figure which shows the example of the irradiation region of a laser beam 12 and the flow path of a particle 1. It is a figure which shows the method of calculating the shift amount Δs from the center of the irradiation region of a laser beam. It is a flowchart which shows an example of the processing content of the analyzer of this embodiment. It is a figure which shows an example of the estimation of the scattered light of a black carbon particle. It is a flowchart which shows an example of the method of calculating the shift amount Δs from the center of the irradiation region of a laser beam. It is a flowchart which shows an example of the process of correcting an analysis result. It is a flowchart which shows another example of the process which corrects an analysis result. It is a flowchart which shows another example of the process which corrects an analysis result. It is a flowchart which shows another example of the process which corrects an analysis result. It is a figure which shows the 1st modification of the 2nd detection part 40. It is a figure which shows the 2nd modification of the 2nd detection part 40. It is a figure which shows the 3rd modification of the 2nd detection part 40. It is a figure which shows the 4th modification of the 2nd detection part 40.

Hereinafter, the present invention will be described through embodiments of the invention, but the following embodiments do not limit the inventions claimed in the claims. Also, not all combinations of features described in the embodiments are essential to the means of solving the invention.

In the present specification, technical matters may be described using orthogonal coordinate axes of the X-axis, the Y-axis, and the Z-axis. In the present specification, the irradiation direction of the laser beam is defined as the X-axis, and the central axis direction of the particle flow path is defined as the Y-axis direction. The direction perpendicular to the X-axis and the Y-axis is defined as the Z-axis direction.

FIG. 1 is a diagram showing a schematic configuration of an analyzer 100 according to an embodiment of the present invention. The analyzer 100 analyzes the particles 1 based on the scattered light 13 generated by the particles 1 contained in the gas scattering the laser light 12. Further, the analyzer 100 may analyze the particles 1 based on the incandescent light 14 which is the light emitted by the particles 1 heated by the laser beam. The analyzer 100 may detect the number of particles 1, the particle size, the mass concentration, and the like.

The particles 1 may be fine particles in a gas. Fine particles in a gas are called aerosols. The particle size of the particles 1 may be 1 μm or more and 100 μm or less, and more specifically, 5 μm or more and 100 μm or less. The average particle size of the particles may be about 10 μm.

Particle 1 may be black carbon (soot). The measurement of black carbon (soot) generated when carbon-based fuel is incompletely burned, such as diesel engine exhaust gas, coal combustion, forest fire, combustion of fuel such as firewood and biomass fuel, is combustion. It is important as an indicator of efficiency.

Black carbon has the property of absorbing light well and being heated. Therefore, when the black carbon is irradiated with a powerful laser beam 12 such as a laser cavity or a pulse laser, the black carbon is instantaneously heated and vaporized. The heated black carbon generates incandescent light 14 by blackbody radiation. By detecting the incandescent light 14, the number of black carbon particles and the size of the particles 1 can be known. This method of detecting the incandescent light of black carbon is called a laser-induced incandescent method (LII method).

The wavelength of the laser beam 12 used in the LII method is a wavelength in the near infrared region. For example, as the laser irradiation unit 10 that generates the laser beam 12, a YAG laser that generates the laser beam 12 having a wavelength of 1064 nm is used. However, the laser irradiation unit 10 is not limited to the YAG laser, and for example, an Nd: YVO4 laser is used as the laser irradiation unit 10.

The analyzer 100 includes a laser irradiation unit 10, an introduction unit 20, a first detection unit 30, a second detection unit 40, and an incandescent light detection unit 50. The laser irradiation unit 10 irradiates the sample gas containing the particles 1 introduced into the analyzer 100 with the laser beam 12. In this example, the beam of the laser beam 12 extends along the X-axis direction.

The laser irradiation unit 10 irradiates the sample air containing the particles 1 introduced into the analyzer 100 with the laser beam 12. The laser irradiation unit 10 may include a light source using an Nd: YVO4 laser. Further, a mirror 11 for forming a laser resonator may be provided at the end opposite to the light source. The wavelength of the laser beam 12 is, for example, 1064 nm.

The introduction unit 20 introduces a gas containing particles 1 to be measured into the laser beam 12. The introduction unit 20 may include a nozzle for transporting the particles 1. The introduction unit 20 may be provided with a rating device for selecting the particle size of the particles 1 to be introduced. In FIG. 1, the gas passage is extended in the Z-axis direction parallel to the paper surface, but it is preferably extended in the Y-axis direction orthogonal to the paper surface. That is, it is desirable that the central axis direction 21 of the flow path is the Y-axis direction. This is to avoid interference between the optical paths of incandescent light and scattered light and the introduction unit 20. In this case, the particles 1 are included in the air flow along the Y-axis direction and pass through the irradiation region of the laser beam 12.

In the LII method, black carbon particles can be selectively measured mainly by measuring incandescent light in the wavelength range of visible light. On the other hand, by removing the light in the visible light wavelength band with a filter, it is possible to receive the scattered light generated when the particles 1 pass through. Since the scattered light is generated from all the particles 1, it is possible to measure the total amount of the particles that have passed through.

In addition, since the scattered light response can be calculated exactly by the Mie scattering theory, it is possible to obtain information on various particles 1 such as the shape in addition to the size of the particle 1. Regarding the black carbon particles, the scattered light changes with time due to the sublimation of carbon and the reduction or disappearance of the particles 1 when passing through the irradiation region of the laser beam 12. Therefore, by correcting the signal of the scattered light, it is possible to analyze the black carbon particles based on the scattered light.

In the LII method, in principle, in order to detect the particles 1 containing all the black carbon, it is necessary to converge and pass the particles 1 in a region narrower than the width of the laser beam 12. When the beam diameter of the laser beam 12 is defined by the width at the intensity when the peak intensity value drops to 1 / e ² , for example, the particle 1 is converged and passed through in a range of 1/2 or less of the beam diameter. Is desirable.

In order to accurately measure the number, particle size, mass concentration, etc. of the particles 1, it is desirable that the central axis of the flow path of the particles 1 and the center of the optical axis of the laser beam 12 intersect at one point. In order to measure the number, particle size, mass concentration, etc. of the particles 1 based on the incandescent light and the scattered light, ideally, each particle is experienced before passing through the irradiation region of the laser beam 12. It is desirable that the laser beam intensity is constant. However, the light intensity of the laser beam 12 is not uniform in the irradiation region, and the center is higher than the periphery. Therefore, since the position where the particle 1 passes through the laser beam irradiation region is different for each particle 1, the laser beam intensity experienced before passing through the laser beam irradiation region is different for each particle 1.

In a system where the central axis of the flow path of the particle 1 and the center of the optical axis of the laser beam 12 intersect at one point, the particle 1 passing through the central axis of the flow path produces the maximum intensity of scattered light and incandescent light, and the central axis of the flow path. When the particle 1 passes through a position deviated from the position, the light intensity of scattered light and incandescent light decreases as compared with the case where the particle 1 passes through the central axis of the flow path regardless of the deviating direction. On the other hand, when the central axis of the flow path of the particle 1 and the center of the optical axis of the laser beam 12 do not intersect at one point, when the particle 1 passes through a position deviated from the central axis of the flow path, depending on the direction of deviation. There are cases where the light intensity of scattered light and incandescent light increases and cases where the light intensity decreases as compared with the case where the particles 1 pass through the central axis of the flow path. Therefore, the accuracy of the number, particle size, mass concentration, etc. of the particles 1 is lower than that of the system in which the central axis of the flow path of the particles 1 and the center of the optical axis of the laser beam 12 intersect at one point.

When the particle size of the particles 1 becomes 1 μm or more and the mass increases, the viscous effect of the surrounding gas decreases, so that the particles 1 do not follow the air flow. Therefore, when the particle size of the particle 1 is 1 μm or more, particularly 5 μm or more, the convergence of the flow path of the particle 1 is lowered. According to the analyzer 100 of the present embodiment, the analysis accuracy is reduced even when the convergence of the flow path of the particles 1 is lowered in the particles 1 having a particle size of 1 μm or more and 100 μm or less, particularly 5 μm or more and 100 μm or less. Suppresses the decrease.

The first detection unit 30 detects the scattered light 13. A plurality of first detection units 30 may be provided. The second detection unit 40 detects that the spot image due to the scattered light moves a predetermined distance on the light receiving surface. The details of the second detection unit 40 will be described later. The incandescent light detection unit 50 detects the light emitted by the particles 1 heated by the laser light 12. The first detection unit 30 and the second detection unit 40 may each include an avalanche photodiode (APD) having detection sensitivity with respect to the wavelength of scattered light. The incandescent photodetector 50 may include a light receiving element such as a photodiode or a phototransistor having detection sensitivity for visible light, for example, light having a wavelength of 630 nm or more and 800 nm or less.

A condenser lens 22, an objective lens 23, and a filter 24 may be provided between the incident surfaces of the first detection unit 30 and the second detection unit 40 and the laser beam 12. The filter 24 may be provided between the condensing lens 22 and the objective lens 23. The filter 24 blocks, for example, incandescent light in the wavelength range of visible light and transmits scattered light in the wavelength range of the near infrared region.

A condenser lens 25, an objective lens 26, and a filter 27 may be provided between the incident surface of the incandescent light detection unit 50 and the laser beam 12. The filter 27 may be provided between the condensing lens 25 and the objective lens 26. The filter 27 may transmit incandescent light in the wavelength range of visible light and block scattered light in the wavelength range of the near infrared region.

The analyzer 100 includes a calculation unit 60 and a correction unit 70. The calculation unit 60 and the correction unit 70 may be configured as a part of the functions of the processing unit 80. The processing unit 80 may be a computer. The calculation unit 60 acquires the detection results from the first detection unit 30, the second detection unit 40, and the incandescent light detection unit 50. The calculation unit 60 calculates the distance that the particle 1 has passed through the irradiation region of the laser beam 12 from the detection result by the first detection unit 30 and the detection result by the second detection unit 40.

The calculation unit 60 may include a first calculation unit 62 and a second calculation unit 64. The first calculation unit 62 acquires the detection result by the first detection unit 30. The first calculation unit 62 calculates the time required for the particle 1 to pass through the irradiation region of the laser beam 12 from the detection result by the first detection unit 30. The second calculation unit 64 calculates the velocity of the particle 1 from the detection result by the second detection unit 40. The calculation unit 60 calculates the distance that the particle 1 has passed through the irradiation region of the laser beam 12 from the time required for the particle 1 to pass through the irradiation region of the laser beam 12 and the velocity of the particle 1.

The correction unit 70 corrects the analysis result of the particle 1 based on the distance that the particle 1 has passed through the irradiation region of the laser beam 12. The correction unit 70 may include a first correction unit 72 and a second correction unit 74. The first correction unit 72 corrects the analysis result based on the scattered light. The second correction unit 74 corrects the analysis result based on the incandescent light.

FIG. 2 is a diagram showing an example of the configuration of the first detection unit 30 and the second detection unit 40. The second detection unit 40 has two photoelectric conversion regions 41, a photoelectric conversion region 42, and a dead zone 43. The dead zone 43 is a dead zone sandwiched between the two photoelectric conversion regions 41 and the photoelectric conversion region 42. The photoelectric conversion regions 41 and 42 convert light into an electric signal. The photoelectric conversion regions 41 and 42 may be avalanche photodiode (APD) portions. In other words, the second detection unit 40 may be an APD element divided into two or more regions. On the other hand, the dead zone 43 does not convert light into an electrical signal. In one example, the second detection unit 40 is a light receiving element having photoelectric conversion regions 41 and 42 divided into at least two or more. As the light receiving element, for example, C30927EH-01 manufactured by Excelitas.

In this example, the dead zone 43 is a detection region for detecting that the spot image 2 of the particles 1 due to scattered light moves a predetermined distance on the light receiving surface. The photoelectric conversion region 41, the dead zone 43, and the photoelectric conversion region 42 may be arranged in this arrangement order in the Y-axis direction. The dead zone 43 intersects the traveling direction of the particle 1. The width Δd of the dead zone 43 in the Y-axis direction, which is the traveling direction of the particles 1, is narrower than the width L of the first detection unit 30 in the Y-axis direction. The width Δd may be 10 μm or more and 300 μm, and may be 100 μm or more and 300 μm.

The analyzer 100 includes a difference calculation unit 51. The difference calculation unit 51 calculates the difference between the detection results in the two photoelectric conversion regions. In this example, the difference between the detection result in the photoelectric conversion region 41 and the detection result in the photoelectric conversion region 42 is calculated. The difference calculation unit 51 may include IV conversion units 52 and 53, a non-inverting amplifier circuit 54, an inverting amplifier circuit 55, and an addition circuit 56. The IV conversion unit 52 converts a current corresponding to the light intensity of the scattered light 13 received by one of the photoelectric conversion regions 41 into a voltage. The IV conversion unit 53 converts a current corresponding to the light intensity of the scattered light 13 received by the other photoelectric conversion region 42 into a voltage.

The non-inverting amplifier circuit 54 does not invert one of the outputs of the IV conversion unit 52 and the IV conversion unit 53. The inverting amplifier circuit 55 inverts the other of the outputs of the IV conversion unit 52 and the IV conversion unit 53. The adder circuit 56 adds the outputs of the non-inverting amplifier circuit 54 and the inverting amplifier circuit 55. As a result, the difference calculation unit 51 calculates the difference between the detection results in the two photoelectric conversion regions 41 and 42. The calculated difference is output to the first calculation unit 62. Common mode noise can be canceled by inverting one of the outputs of the IV conversion unit 52 and the IV conversion unit 53 and then adding the output.

On the other hand, the detection result of the first detection unit 30 may be output to the first calculation unit 62 via the IV conversion unit 31 and the amplifier circuit 33. The calculation unit 60 may calculate the distance that the particle 1 has passed through the irradiation region of the laser beam 12 from the detection result by the first detection unit 30 and the difference result by the difference calculation unit 51.

FIG. 3 is a diagram illustrating an example of a first detection signal obtained by the first detection unit 30. FIG. 4 is a diagram illustrating an example of a second detection signal obtained by the second detection unit 40. In FIGS. 3 and 4, the objective lens 23 and the filter 24 are omitted. The light intensity of the laser beam 12 is not uniform in the irradiation region, and the light intensity becomes weaker as the first region 12a, the second region 12b, and the third region 12c become from the center to the periphery. The outer edge of the third region 12c is shows a 1 / ^{e 2} beam diameter of the laser beam 12. Then, the range of 1 / e ² beam diameter may be used as the irradiation region.

When the particles 1 are present in the irradiation region of the laser beam 12, the particles 1 generate scattered light 13. The scattered light 13 is condensed by the condensing lens 22 and forms a spot image 2 on the light receiving surface 34 of the first detection unit 30. Then, the spot image 2 moves on the light receiving surface 34 in the direction opposite to the traveling direction of the particles 1. The detection result by the first detection unit 30 is output as the first detection signal 36. The first detection signal 36 corresponds to the output value of the first detection unit 30 at the time. The first detection signal 36 is an APD signal obtained by photoelectric conversion by, for example, an avalanche photodiode (APD). The first detection signal 36 may be a signal obtained via the IV conversion unit 31 and the amplifier circuit 33. The first detection signal 36 shows a curve similar to a Gaussian function.

On the other hand, the scattered light 13 is condensed by the condensing lens 22 and forms a spot image 2 corresponding to the particles 1 on the light receiving surface 44 of the second detection unit 40. The spot image 2 moves on the light receiving surface 44 in the direction opposite to the traveling direction of the particles 1. The spot image 2 on the light receiving surface 44 of the scattered light moves across the divided photoelectric conversion regions 41 and 42 as the particles 1 pass through the laser beam 12 irradiation region. The detection result by the second detection unit 40 is output as the second detection signal 46. As described above, the second detection signal 46 may be the difference between the detection results in the two photoelectric conversion regions 41 and 42. The difference may be calculated by combining the output from the photoelectric conversion region 41 as negative and the output from the photoelectric conversion region 42 as positive. The second detection signal 46 is also called a divided APD signal obtained by photoelectric conversion by a divided avalanche photodiode (APD).

FIG. 5 shows a method of calculating the velocity of the particle 1 based on the detection signal. The second detection signal 46 is obtained by combining the output from the photoelectric conversion region 41 as positive and the output from the photoelectric conversion region 42 as negative. The second detection signal 46 has a zero point due to the presence of the width Δd of the dead zone 43 in the Y-axis direction, which is the traveling direction of the particles 1. If the scattered light of the particles 1 does not scale with respect to the light receiving surface 44 and the optical system forms an image with the same size, the photoelectric conversion region 41 and the photoelectric conversion region 42 are divided by a dead zone 43 (gap). If so, the sign of the second detection signal 46 is reversed when the spot FIG. 2 passes through the gap Δd.

Further, the second calculation unit 64 calculates the equation 1 V _axis = Δd / Δt _dev , assuming that the time required for the particle 1 to pass through the dead zone 43 is Δt _dev, and thereby, the axial direction of the flow path of the particle 1. The velocity component _{Vaxis of} is calculated. Δt _dev is acquired from the second detection signal 46. Specifically, the second calculation unit 64 acquires Δt _dev based on the time between the time of the negative peak and the time of the positive peak in the second detection signal 46. In one example, the second calculation unit 64 may calculate Δt _dev by multiplying the time between the time of the negative peak and the time of the positive peak in the second detection signal 46 by the constant k. The constant k is experimentally or theoretically predetermined. For example, when k = 1, the second calculation unit 64 sets the time between the negative peak time and the positive peak time in the second detection signal 46 as Δt _dev .

FIG. 6 is a diagram showing a method of calculating the laser passing distance from the velocity of the particle 1 and the passing time of the particle 1 in the irradiation region. The first calculation unit 62 calculates the time Δt _Norm required for the particle 1 to pass through the irradiation region of the laser beam 12 from the detection result by the first detection unit 30. Specifically, the time width Δt _Norm of the first detection signal 36 corresponds to the time required to pass through the irradiation region of the laser beam 12. Therefore, the first calculation unit 62 may calculate the period in which the detection result by the first detection unit 30 shows a value equal to or more than a predetermined threshold value as the time width Δt _Norm . The threshold value may be, for example, a value that is 1 / e ² of the peak value.

Calculating unit 60 calculates a time Delta] t _Norm taken irradiation region to pass the particle 1, and a velocity _{V axis} of the particle 1, the distance _{d Laser} particle 1 irradiation region of the laser beam 12 has passed To do. Calculator 60 calculates, for example, the distance _{d Laser} multiplied by _{V axis} in time Delta] t _Norm.

FIG. 7 is a diagram showing an example of the irradiation region of the laser beam 12 and the flow path of the particle 1. In the flow path 28, the ratio of the particles 1 passing through the central region 28a of the flow path of the particles 1 is larger than the ratio of the particles 1 passing through the peripheral portion. However, it is difficult to completely limit the flow path 28 of the particle 1. Therefore, the passing position may be different for each particle 1. The closer the position through which the particle 1 passes to the center of the laser beam 12, the longer the distance d _Laser through which the particle 1 passes within the irradiation region of the laser beam 12. In other words, when the position where the particle 1 passes passes through the center of the laser beam 12, the distance d _Laser becomes equal to the beam diameter of the laser beam 12. On the other hand, when the distance d _Laser is smaller than the beam diameter of the laser beam 12, it indicates that the position where the particle 1 passes has passed a path off the center of the laser beam 12.

In the case shown in FIG. 7, _dLaser 1 is longer than _dLaser 2. Therefore, the distance between the center of the irradiation region of the laser beam and the passage path of the particle 1 can be calculated by using the distance d _Laser that the particle 1 has passed through the irradiation region of the laser beam 12.

FIG. 8 is a diagram showing a method of calculating the shift amount Δs from the center of the irradiation region of the laser beam 12. In other words, the shift amount Δs is the shift amount from the beam center of the laser beam 2. The shift amount Δs means the distance between the center of the irradiation region of the laser beam 12 and the passage path of the particles. The beam diameter D _Laser of the laser beam 12 is determined by the characteristics of the laser beam 12. The calculation unit 60 calculates the shift amount Δs by the following formula using the beam diameter D _Laser of the laser beam 12 and _the above distance d _Laser .

The history of the beam intensity experienced by the particle 1 can be calculated from the shift amount Δs from the beam center and the light intensity distribution (laser beam profile) in the irradiation region of the laser light. The light intensity distribution in the irradiation region of the laser beam is measured using a beam profiler (not shown) incorporating an image sensor. For example, a beam profiler is installed behind the mirror 11 that constitutes the laser resonator. Then, the beam profiler observes the light intensity distribution in the irradiation region of the laser light from the leaked light leaking to the outside of the laser resonator. In that case, it is necessary to estimate the strength near the center of the resonator. The intensity near the center of the resonator can be calculated from the Hermitian Gaussian mode (Hemite-Gaussian mode) or the like.

The correction unit 70 corrects the analysis result of the particle 1 based on the distance that the particle 1 has passed through the irradiation region of the laser beam 12. Specifically, the correction unit 71 may calculate the shift amount Δs by using the distance d _Laser that the particle 1 has passed through the irradiation region of the laser beam 12 as described above. The history of the beam intensity experienced by the particle 1 is calculated from the shift amount Δs and the light intensity distribution in the irradiation region acquired separately. Based on the calculated beam intensity history, the correction unit 70 determines the particle 1 from the intensity ratio between the case where the particle 1 passes through the position of the shift amount Δs and the case where the particle 1 passes through the central portion of the optical axis of the laser beam 12. Correct the analysis result of. Therefore, it is possible to detect the particle size with high accuracy and calculate the amount of black carbon.

The correction unit 70 may correct the analysis result of the particle 1 from the above-mentioned intensity ratio and the like. However, the correction unit 70 is not limited to the one that executes such a process. The correction unit 70 may correct the analysis result of the particle 1 by using the distance d _Laser that the particle 1 has passed through the irradiation region of the laser beam 12.

FIG. 9 is a flowchart showing an example of the processing contents of the analyzer of the present embodiment. The first detection unit 30 receives the scattered light 13. The first detection unit 30 photoelectrically converts the scattered light 13 into an electric signal. As a result, the first detection signal 36 is obtained (step S101). The second detection unit 40 photoelectrically converts the scattered light 13 into an electric signal (step S102). The dead zone 43 provided in the second detection unit 40 detects that the spot image due to the scattered light moves a predetermined distance on the light receiving surface 44. The incandescent light detection unit 50 receives the incandescent light 14 emitted by the particles 1 heated by the laser light 12 (step S103). The incandescent light detection unit 50 photoelectrically converts the incandescent light 14 into an electric signal. The processes of steps S101 to S103 may be executed in parallel.

The second calculation unit 64 calculates the velocity of the particle 1 from the detection result by the second detection unit 40 (step S104). The processing unit 80 determines whether or not the particles 1 are black carbon particles 1 (step S105). When the incandescent light detection unit 50 detects the incandescent light 14, the processing unit 80 may determine that the particles 1 are black carbon particles. When the particle 1 is a black carbon particle (step S105: YES), when the particle 1 passes through the irradiation region of the laser beam 12, the carbon sublimates and the particle 1 shrinks or disappears. Therefore, the processing unit 80 may estimate the scattered light of the black carbon particles (step S106).

FIG. 10 is a diagram showing an example of estimation of scattered light of black carbon particles. The scattered light detection signal 37 when the particle 1 is black carbon includes notches 39a and 39b caused by the dead zone 43. The time of the notches 39a and 39b gives information on the position of the particle 1. For example, the position of the particle 1 is determined based on the time of the notch portions 39a and 39b and the velocity of the particle calculated separately. The processing unit 80 may estimate the scattered light of the black carbon particles by fitting to a Gauss curve using the information on the positions of the initial rising portion 38 and the particles 1 obtained from the notch portions 39a and 39b.

In FIG. 9, the processing unit 80 calculates the shift amount Δs from the center of the irradiation region of the laser beam (step S107). The processing unit 80 calculates the history of the beam intensity experienced by the particle 1 (step S108). The correction unit 70 corrects the analysis result of the particle 1 based on the distance that the particle 1 has passed through the irradiation region of the laser beam 12 (step S109). Specifically, the correction unit 70 may correct the analysis result based on the history of the beam intensity experienced by the particle 1 calculated based on the shift amount Δs.

FIG. 11 is a flowchart showing an example of a method of calculating the shift amount Δs from the center of the irradiation region of the laser beam 12. The first calculation unit 62 calculates the time Δt _Norm required for the particle 1 to pass through the irradiation region of the laser beam 12 from the first detection signal 36 (step S201).

Calculating unit 60 calculates a time Delta] t _Norm taken irradiation region to pass the particle 1, and a velocity _{V axis} of the particle 1, the distance _{d Laser} particle 1 irradiation region of the laser beam 12 has passed (Step S202). Calculator 60 calculates, for example, the distance _{d Laser} multiplied by _{V axis} in time Delta] t _Norm. The calculation unit 60 may calculate the shift amount Δs by using the beam diameter D _Laser of the laser beam 12 and _the above-mentioned distance d _Laser .

FIG. 12 is a flowchart showing an example of processing for correcting the analysis result. In the example shown in FIG. 12, the processing unit 80 calculates the particle size of the particles based on the detection result of the scattered light detected by the first detection unit 30. The first correction unit 72 corrects the particle size of the particle 1 calculated based on the detection result of the scattered light 13. The first correction unit 72 may use the shift amount Δs. The history of the beam intensity experienced by the particle 1 is calculated from the shift amount Δs and the light intensity distribution in the irradiation region acquired separately. Based on the history of the beam intensity, the first correction unit 72 determines the particle size from the intensity ratio between the case where the particle 1 passes through the position of the shift amount Δs and the case where the particle 1 passes through the central portion of the optical axis of the laser beam 12. May be corrected. The first correction unit 72 may have a table showing the relationship between the strength ratio and the correction amount of the particle size. The first correction unit 72 may correct the particle size with reference to the table.

FIG. 13 is a flowchart showing another example of the process of correcting the analysis result. The first correction unit 72 corrects the detection result of the scattered light 13 (step S401). In particular, the first correction unit 72 determines the intensity when the particle 1 passes through the position of the shift amount Δs and when it passes through the central portion of the optical axis of the laser beam 12 based on the calculated history of the beam intensity. The actual first detection signal 36 is corrected from the ratio. In one example, the first correction unit 72 acquires the first detection signal 36 when the particle 1 passes through the center of the optical axis of the laser beam 12. The processing unit 80 calculates the particle size of the particle 1 based on the corrected first detection signal 36.

FIG. 14 is a flowchart showing another example of the process of correcting the analysis result. The first correction unit 72 selects the particles 1 that have passed through a predetermined region within the irradiation region of the laser beam 12 based on the distance d _Laser that the particles 1 have passed through the irradiation region of the laser beam 12 (step). S501). For example, the first correction unit 72 selects the particles 1 that have passed through the region near the center of the irradiation region of the laser beam 12. Specifically, the first correction unit 72 selects the particles 1 when the distance d _Laser is equal to or longer than a predetermined length. Alternatively, the calculation unit 60 calculates the shift amount Δs based on the distance d _Laser . The first correction unit 72 selects the particles 1 when Δs is equal to or less than a predetermined value.

The first correction unit 72 may analyze the particles 1 selected as the particles 1 that have passed through the predetermined region (step S502). The first correction unit 72 may not analyze the excluded particles 1. This makes it possible to reduce the error that occurs in the analysis result. By selecting in this way, it can be said that the detection result including a large error is removed, and as a result, the analysis result of the particle 1 is corrected.

FIG. 15 is a flowchart showing another example of the process of correcting the analysis result. The second correction unit 74 corrects the detection result by the incandescent light detection unit based on the distance d _Laser that the particle 1 has passed through the irradiation region of the laser light 12 (step S601). The second correction unit 74 passed the case where the particle 1 passed the position of the shift amount Δs and the central portion of the optical axis of the laser beam 12 based on the history of the beam intensity calculated using the distance d _Laser . The detection result by the incandescent light detector is corrected from the intensity ratio with the case.

When the particle 1 is, for example, a black carbon particle, the particle 1 heated by the laser beam 12 generates incandescent light 14 by blackbody radiation. However, since the center of the optical axis of the laser beam 12 has a higher light intensity than the peripheral portion, the temperature at which the particle 1 is heated decreases as the shift amount Δs from the center of the irradiation region of the laser beam increases, resulting in incandescent light. The light receiving intensity of 14 becomes weak. Therefore, the size of the particle 1 may be calculated to be smaller than the actual size.

Therefore, the second correction unit 74 may correct the intensity of the detection result by the incandescent light detection unit based on the distance d _Laser or the shift amount Δs. The processing unit 80 may detect the number of particles and the particle size of the black carbon particles based on the corrected detection result. The second correction unit 74 may store in advance the relationship between the shift amount Δs and the correction amount of the particle size as a table. The second correction unit 74 may calculate the correction amount of the particle diameter corresponding to the shift amount Δs with reference to the table. Further, the second correction unit 74 may select the particles 1 that have passed through a predetermined region within the irradiation region of the laser beam 12 based on the distance d _Laser . Then, the particle size and the like may be calculated for the selected particles 1.

From the above, it is possible to calculate the history of the beam intensity experienced by the particle 1 based on the estimated beam intensity, and when the central axis of the particle flow path and the center of the laser optical axis do not match, and the detection region of the particle 1. Even when the convergence in is deteriorated, it is possible to correct from the intensity ratio when passing through the central part based on the history of beam intensity, so highly accurate particle size detection and black carbon can be detected. The amount can be calculated.

In the above-mentioned example, the case where the dead zone 43 sandwiched between the two photoelectric conversion regions 41 and the photoelectric conversion region 42 is used as the detection region has been described. However, the analyzer 100 of the present embodiment is not limited to this case. The second detection unit 40 may have a detection region for detecting that the spot image due to the scattered light 16 moves a predetermined distance on the light receiving surface.

FIG. 16 is a diagram showing a first modification of the second detection unit 40. In this example, the second detection unit 40 is provided with a photoelectric conversion region 47 as a detection region for detecting that the spot image due to the scattered light 16 moves a predetermined distance on the light receiving surface. The photoelectric conversion region 47 converts scattered light into an electric signal. The width Δd of the photoelectric conversion region 47 in the Y-axis direction, which is the traveling direction of the particles 1, is narrower than the width L of the first detection unit 30 in the Y-axis direction. The width Δd may be 10 μm or more and 300 μm, and may be 100 μm or more and 300 μm.

FIG. 17 is a diagram showing a second modification of the second detection unit 40. In this example, the second detection unit 40 includes a plurality of photoelectric conversion regions 48a, 48b, 48c, 48d for converting light into an electric signal, and a plurality of dead zones 49a, 49b, 49c. A plurality of photoelectric conversion regions 48a, 48b, 48c, 48d and a plurality of dead zones 49a, 49b, 49c are alternately arranged one by one. In addition, also in FIG. 17, a plurality of difference calculation units 51 shown in FIG. 2 may be provided. Specifically, the plurality of difference calculation units 51 display the detection results between the two adjacent photoelectric conversion regions 48a and 48b, between the two photoelectric conversion regions 48b and 48c, and between the photoelectric conversion regions 48c and 48d, respectively. Calculate the difference.

The dead zones 49a, 49b, 49c sandwiched between the two photoelectric conversion regions 48a and 48b, between the two photoelectric conversion regions 48b and 48c, and between the two photoelectric conversion regions 48c and 48d, respectively, are used as detection regions. Function. The second calculation unit 64 may calculate the velocity of the particle 1 by using the detection results of each of the plurality of detection regions. In one example, the velocity of the particle 1 may be calculated from the detection results of each detection region, and the velocity obtained by averaging the calculated velocities may be defined as the velocity of the particle 1. This improves the measurement accuracy.

The plurality of dead zones 49a, 49b, 49c may be a plurality of dead zones having different widths in the traveling direction of the particles 1. For example, the widths of the dead zones 49a, 49b, 49c may be Δd1, Δd2, and Δd3, respectively. Δd1 <Δd2 <Δd3 may be satisfied. According to such a configuration, three sets of negative peaks and positive peaks shown in FIG. 5 are obtained according to the difference in width of Δd1, Δd2, and Δd3, and the negative peaks and positive peaks in each set are positive. The time intervals between peaks are different from each other. Therefore, information on the position of the particle 1 in the irradiation region of the laser beam 12 can be obtained from each of the second detection signals 46.

FIG. 18 is a diagram showing a third modification of the second detection unit 40. In the example shown in FIG. 18, another photoelectric conversion region 45 is provided in place of the dead zone 43 in the example shown in FIG. The other photoelectric conversion region 45 is sandwiched between the two photoelectric conversion regions 41 and the photoelectric conversion region 42. The other photoelectric conversion region 45 may have different photoelectric conversion characteristics from the two photoelectric conversion regions 41 and the photoelectric conversion region 42, and may have the same photoelectric conversion characteristics.

The connection between the two photoelectric conversion regions 41 and the photoelectric conversion region 42 and the difference calculation unit 51 is the same as in the case shown in FIG. Common mode noise can be canceled by inverting and adding one of the outputs of the two photoelectric conversion regions 41 and the photoelectric conversion region 42. On the other hand, the velocity of the particle 1 can be calculated from the detection result in the photoelectric conversion region 45 as in the case shown in FIG. Since the velocity of the particle 1 can be calculated by a plurality of methods, the accuracy can be improved.

FIG. 19 is a diagram showing a fourth modification of the second detection unit 40. In this example, a first detection region extending along the first direction and a second detection region extending along the second direction are included. In this example, the photoelectric conversion regions 41a, 41b, 42a, and 42b divided into four are provided. A dead band 43a that partitions the set of photoelectric conversion regions 41a and 41b and the set of 42a and 42b in the Y-axis direction is provided. On the other hand, a dead zone 43b that divides the photoelectric conversion regions 41a and 42a and 41b and 42b in the X-axis direction is provided.

In this example, the dead zone 43a is the first detection region, and the dead zone 43b is the second detection region. The second calculation unit 64 is based on the detection results in the first detection region (dead zone 43a in this example) and the second detection region (dead zone 43b in this example) in the second detection unit 40, and the first direction component of the velocity of the particle 1 is obtained. (Y-axis direction component) and second direction component (X-direction component) are calculated.

In this example, the central axis direction 21 of the flow path of the particle 1 is the Y-axis direction. The dead zone 43a, which is the first detection region, divides the set of photoelectric conversion regions 41a and 41b and the set of photoelectric conversion regions 42a and 42b in the central axial direction 21 of the flow path of the particle 1. One set of the photoelectric conversion regions 41a and 41b and the pair of the photoelectric conversion regions 42a and 42b may be inverted so that the polarities of the outputs are opposite to each other. On the other hand, the photoelectric conversion regions 41a and 41b may be connected so as to have the same polarity, and the photoelectric conversion regions 42a and 42b may be connected so as to have the same polarity. Such a configuration is advantageous in calculating the velocity component _Vaxis in the axial direction of the flow path of the particle 1.

Further, in the photoelectric conversion regions 41a and 42a and 41b and 42b divided into four, the photoelectric conversion region 41a has a positive polarity (non-inverted) and the photoelectric conversion region 42a has a negative polarity (inverted). May have a positive polarity (non-inverted) and the photoelectric conversion region 41a may have a negative polarity (inverted). In this case, the difference in the output result between the photoelectric conversion region 41a and the photoelectric conversion region 42a, the difference in the output result between the photoelectric conversion region 42a and the photoelectric conversion region 42b, and the photoelectric conversion region 42b and the photoelectric conversion region 41b. The difference of the output result between them and the difference of the output result between the photoelectric conversion area 41b and the photoelectric conversion area 41a are calculated by each difference calculation unit 51.

In the case of this example, since the first direction component (Y-axis direction component) and the second direction component (X-direction component) of the velocity of the particle 1 can be obtained, the particle 1 is in the flow path as shown in FIG. Even when passing through the irradiation region of the laser beam 12 with an inclination with respect to the central axis direction 21 (Y-axis direction), the distance d _Laser that the particle 1 has passed through the irradiation region of the laser beam 12 is accurately calculated. can do. Therefore, the shift amount Δs from the center of the irradiation region of the laser beam can also be calculated accurately. As a result, the correction unit 70 can correct the analysis result of the particle 1 more accurately.

As is clear from the above, according to the analyzer 100, even when the central axis of the particle flow path and the center of the laser optical axis do not match, or when the convergence in the detection region of the particle 1 is lowered, the influence is eliminated. Or it can be reduced.

Although the present invention has been described above using the embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments. It will be apparent to those skilled in the art that various changes or improvements can be made to the above embodiments. For example, the processing unit 80 may adjust the optical axis of the laser beam 12 based on the amount of shift from the center of the beam. It is clear from the description of the claims that the form with such changes or improvements may be included in the technical scope of the present invention. The present invention can also be used in an analyzer that analyzes particles by scattered light that does not use incandescent light.

The order of execution of each process such as operation, procedure, step, and step in the device, system, program, and method shown in the claims, specification, and drawings is particularly "before" and "prior to". It should be noted that it can be realized in any order unless the output of the previous process is used in the subsequent process. Even if the scope of claims, the specification, and the operation flow in the drawings are explained using "first," "next," etc. for convenience, it means that it is essential to carry out in this order. It's not a thing.

1 ... Particles, 10 ... Laser irradiation part, 11 ... Mirror, 12 ... Laser light, 13 ... Scattered light, 14 ... Incandescent light, 16 ... Scattered light, 20 ... Introduction part, 21 ... Central axis direction of the flow path, 22 ... Condensing lens, 23 ... Objective lens, 24 ... Filter, 25 ... Condensing lens, 26 ... Objective lens, 27 ... Filter, 28 ... Flow path, 30・ ・ 1st detection unit, 31 ・ ・ IV conversion unit, 33 ・ ・ amplification circuit, 34 ・ ・ light receiving surface, 36 ・ ・ 1st detection signal, 37 ・ ・ scattered light detection signal, 38 ・ ・ part, 39 ・ ・Notch part, 40 ... 2nd detection part, 41 ... Photoelectric conversion area, 42 ... Photoelectric conversion area, 43 ... Dead zone, 44 ... Light receiving surface, 45 ... Photoelectric conversion area, 46 ... 2nd detection signal , 47 ... photoelectric conversion area, 48 ... Photoelectric conversion area, 49 ... Dead zone, 50 ... Incandescent light detection unit, 51 ... Difference calculation unit, 52 ... IV conversion unit, 53 ... IV conversion unit, 54・ ・ Non-inverting amplification circuit, 55 ・ ・ Inversion amplification circuit, 56 ・ ・ Addition circuit, 60 ・ ・ Calculation unit, 62 ・ ・ 1st calculation unit, 64 ・ ・ 2nd calculation unit, 70 ・ ・ Correction unit, 71 ・・ Correction unit, 72 ・ ・ 1st correction unit, 74 ・ ・ 2nd correction unit, 80 ・ ・ Processing unit, 100 ・ ・ Analyzer

Claims (15)

An analyzer that analyzes the particles based on the scattered light generated by the particles scattering the laser light.
The first detection unit that detects the scattered light and
A second detection unit provided with a detection region for detecting that the spot image due to the scattered light moves a predetermined distance on the light receiving surface, and
A calculation unit that calculates the distance that the particles have passed through the irradiation region of the laser beam from the detection result by the first detection unit and the detection result by the second detection unit.
An analyzer equipped with. The calculation unit
From the detection result by the first detection unit, the first calculation unit that calculates the time required for the particles to pass through the irradiation region of the laser beam, and
Includes a second calculation unit that calculates the velocity of the particles from the detection result by the second detection unit.
The calculation unit calculates the distance that the particles have passed through the irradiation region of the laser beam from the time required for the particles to pass through the irradiation region and the velocity of the particles. Item 1. The analyzer according to item 1. The analyzer according to claim 2, wherein the detection region has a narrower width in the traveling direction of the particles than the first detection unit. The analyzer according to claim 2 or 3, wherein the detection region is a photoelectric conversion region that converts light into an electric signal. The analyzer according to claim 2 or 3, wherein the detection region is a dead zone sandwiched between two photoelectric conversion regions that convert light into an electric signal. The second detection unit includes a plurality of photoelectric conversion regions for converting light into an electric signal and a plurality of dead zones.
The analyzer according to claim 5, wherein a plurality of photoelectric conversion regions and a plurality of dead zones are alternately arranged one by one. The analyzer according to claim 6, wherein the plurality of dead zones include a plurality of dead zones having different widths in the traveling direction of the particles. The analyzer according to claim 2 or 3, wherein the detection region is another photoelectric conversion region sandwiched between two photoelectric conversion regions that convert light into an electric signal. The analyzer includes a difference calculation unit that takes the difference between the detection results in the two photoelectric conversion regions.
The calculation unit calculates the distance that the particles have passed through the irradiation region of the laser beam from the detection result by the first detection unit and the result of the difference.
The analyzer according to any one of claims 5 to 8. The analyzer according to any one of claims 1 to 9, further comprising a correction unit that corrects the analysis result of the particles based on the distance that the particles have passed through the irradiation region. The analyzer according to claim 10, wherein the correction unit corrects the detection result of the scattered light. The analyzer according to claim 10, wherein the correction unit corrects the particle size of the particles calculated based on the detection result of the scattered light. The correction unit selects the particles that have passed through a predetermined region of the irradiation region of the laser beam based on the distance that the particles have passed through the irradiation region, thereby obtaining the analysis result of the particles. The analyzer according to claim 10, which is amended. An incandescent photodetector that detects the light emitted by the particles heated by the laser beam,
A second correction unit that corrects the detection result by the incandescent light detection unit based on the distance that the particles have passed through the irradiation region is further provided.
The analyzer according to any one of claims 1 to 13. The detection region includes a first detection region extending along the first direction and a second detection region extending along a second direction intersecting the first direction.
2. The second calculation unit calculates the first-direction component and the second-direction component of the velocity of the particles from the detection results in the first detection region and the second detection region in the second detection unit. The analyzer described in.

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