Laser Particle Size Analyzer

Overview

A laser particle size analyzer measures how big the particles in a sample are, the grind of a cement powder, the droplets in an emulsion, the pigment in a paint. It works by laser diffraction: when a parallel laser beam passes through a cloud of particles, each one scatters light into a pattern that depends on its size. Small particles scatter widely, large ones scatter into a tight forward cone. By recording the whole scattering pattern at once and mathematically inverting it, the instrument reports a full size distribution in seconds.

Because it measures thousands of particles in a single illuminated volume, laser diffraction gives statistically robust distributions far faster than sieving or microscopy, which is why it dominates quality control in powders, slurries and sprays.

How it works

The beam starts at the Laser Source & Beam Optics, where a temperature-stabilized laser diode is collimated and expanded into a wide, parallel, monochromatic beam and cleaned by a spatial filter. It then crosses the Sample Dispersion Cell. For suspensions a Recirculation Pump circulates the sample past optical windows while an ultrasonic probe breaks up clumps; for dry powders a Dry Powder Venturi disperses them in an air jet. Good dispersion matters, agglomerates read as single large particles and spoil the result.

Scattered light falls on the Multi-Element Detector Array. A Photodiode Ring of detectors at increasing angles samples the forward-scattered pattern, Scatter Focusing Lens optics map each scattering angle to a radial position, and side and back detectors extend the range to sub-micron particles. Every element is held in fixed alignment on the Optical Bench, a rigid isolated plate that preserves the optical path.

The Control & Computer reads all detector channels simultaneously and inverts the pattern, using Mie theory, into a volume-based size distribution, then reports the familiar Dv10/Dv50/Dv90 percentiles. The Instrument Housing keeps the optical path light-tight and the operator clear of the laser.