1 Introduction

Laser diffraction particle size analyzer, commonly known as "laser particle size analyzer", is a widely used particle size measurement device. Commercial instruments have been available for 50 years, and I have been in the industry for nearly 30 years.

Physical principles: diffraction of light/static light scattering. The scattered light spot presents a central bright spot with a series of concentric bright rings, known as the "Airy Spot". The distance from the center to the dark ring is called the radius of the Airy Spot. The larger the particles, the smaller the size of the Airy Spot.

The average scattering angle and receiving area of the detection unit increase exponentially from the inside out. Therefore, each particle size corresponds to a peak in the distribution of light energy, and the position of the peak shifts from the outside to the inside as the particle size increases.