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In production and scientific research, the research on the characteristics of submicron particles has attracted extensive attention, which is of great significance to the development of industrial production, medical and health inspection and other fields. In this paper, the characteristics of submicron particles are studied based on backlight scattering. By collecting the real-time waveform of the backscattering signal of particles with different particle sizes at different concentrations, the corresponding relationship between the particle concentration and the number of pulses was obtained. It is found that the peak value of the backscattered light energy has a good linear relationship with the particle size. The analysis of the signal distribution law of standard particle swarm with different particle size parameters found that it conformed to the lognormal distribution form.

Submicron particles are widely present in production and daily life [

The experimental system for measuring the backscattering characteristics of particles is shown in

_{G}. The coordinate

system O p x y z is the particle coordinate system, the origin of the coordinate system is at the particle center, the z-axis is parallel to the w axis.

According to the calculation model shown in

E s c a = ∫ α = 0 2 π ∫ ρ = 0 ρ max I s c a ( θ , ϕ ) ρ d ρ d α . (1)

among them

I s c a ( θ , ϕ ) = λ 2 4 π 2 r 2 [ i 1 ( θ , ϕ ) + i 2 ( θ , ϕ ) ] . (2)

In the above formula, i 1 ( θ , ϕ ) and i 2 ( θ , ϕ ) are scattering intensity functions, which can be calculated by GLMT.

The backscattering characteristics of the particles are closely related to the particle size. With different particle sizes, the backscattered light energy is significantly different. Based on the principle of backscattering of particles, a program written by Monte Carlo algorithm is used to calculate the backscattered light energy of the particles, and the corresponding relationship between the scattered light energy of the particles and the particle size is obtained by changing the parameters. Set the beam waist radius of the Gaussian beam to be ω = 5.0 , the wavelength to be λ = 0.6328 , and the refractive index is 1.57, change the particle size. From the simulation calculations, it can be known that the backscattered light energy has a linear relationship of linear micro-oscillation on the logarithmic coordinate as the particle size changes. The line relationship is shown in

The experimental device is built according to the experimental principle of

The standard polystyrene particles with radii of 0.1 μm, 0.2 μm, 0.3 μm, 0.5 μm were measured by the above experimental device, and the pulse waveform signal was obtained. Before putting the particles to be tested, start the peristaltic pump, adjust the photoelectric detector, and reduce the noise.

Under the same experimental conditions, particle samples were gradually added to the cyclic sampling system.

In

the particles is also random, and the amplitude of these pulse signals contains the inherent characteristics of the interaction between the particles and the beam (such as particle size, particle refractive index, etc.).

In this paper, we try to fit the logarithmic normal distribution to the amplitude of the experimental data, equation [

P ( V − V m ) = 1 2 π σ v ( V − V m ) exp [ − ( ln ( V − V m ) − μ v ) 2 2 σ v 2 ] , V ∈ ( V m − V M ) (3)

where V m represents the classification interval of voltage, V represents the voltage value, and P ( V − V m ) represents the probability value between V and V + V m .

Under the same experimental device conditions, random measurement is performed on the standard particles with particle sizes of 0.2 μm, 0.3 μm, and 0.5 μm to obtain 1000 pieces of data respectively, and the peak value of these 1000 pieces of data was counted according to formula (3) using Python language. The data results are shown in

This article introduces a submicron particle test method for detecting backscattered light signals. In the detection device of this method, the incident Gaussian

beam and the scattered beam pass through the same lens, which makes the measurement area independent of the optical device, thereby enhancing the shockproof performance of the measurement device, which is convenient for practical applications.

Through theoretical analysis and experimental research on the backscattering method, the article obtains the variation law between the particle size and particle concentration and the backscattered light energy. When the number of samples is collected enough, the peak distribution of the pulse waveform is analyzed and it is found that the statistical amplitude distribution of the particles agrees well with the lognormal distribution. The experimental measurement shows that the backscattered light energy distribution of the particles has a linear relationship with the particle size and is consistent with the theoretical analysis results, and the number of particle backscattering response signals in the same time period increases with increasing concentration.

The authors declare no conflicts of interest regarding the publication of this paper.

Hou, K.L., Wang, C.W. and Liu, X. (2020) Study on Backward Scattering Characteristics of Submicron Particles. Optics and Photonics Journal, 10, 79-87. https://doi.org/10.4236/opj.2020.105007