The principle of laser particle size analyzer

Laser particle size analyzer is used to test particle size distribution based on the physical phenomenon that particles can cause laser scattering. Due to the excellent monochromaticity and directionality of lasers, they will reach infinity in unobstructed infinite space, and there is little divergence during propagation.

The Mie scattering theory suggests that when a beam of light encounters particle obstruction, a portion of the light will undergo scattering, and the propagation direction of the scattered light will form an angle θ with the propagation direction of the main beam. The size of the θ angle is related to the size of the particles, and the larger the particles, the smaller the θ angle of the scattered light produced; The smaller the particle, the larger the θ angle of the scattered light produced. Small angle (θ) scattered light is caused by large particles; The scattered light at a large angle (θ 1) is caused by small particles. Further research indicates that the intensity of scattered light represents the number of particles of that size. In this way, by measuring the intensity of scattered light at different angles, the particle size distribution of the sample can be obtained.

In order to measure the intensity of scattered light at different angles, optical means need to be used to process the scattered light. We place a Fourier lens at an appropriate position in the beam and a set of multi-element photodetectors on the back focal plane of the Fourier lens. When scattered light from different angles is irradiated onto the multi-element photodetectors through the Fourier lens, the optical signal will be converted into an electrical signal and transmitted to the computer. These signals will be processed by software to accurately obtain the particle size distribution.