Colorado Patent of the Month – March 2021

There are many well known particle size and concentration analysis (PSA) techniques. Most involve optical measurements with laser radiation which result in large inaccuracies. Time of Transition (TOT) is a less sensitive optical technique which uses focused laser beams. With TOT, the particles are analyzed in the time domain rather than in the amplitude domain, resulting in lower sensitivity to variation in the refractive index. The resolution is based on the laser beam width – where smaller particles are measured with a smaller beam focus. However, the width is limited by the wavelength. This leaves a compromise between concentration measurement rate and the quality and resolution of the size analysis. Particle Measuring Systems, Inc. redesigned this technique to use a shorter wavelength of light. This change will increase sensitivity and the ability to measure higher particle concentrations.

The shorter wavelength operates the same for particles on a surface, airborne, or fluid-borne. This PSA uses a laser that generates a Gaussian beam which is converted into a structured dark beam. The dark beam is focused on the particles. Two detectors are positioned relative to the dark beam. 

The invention is a particle monitoring system comprising a laser that generates a Gaussian beam; means for converting the Gaussian laser beam into a structured dark beam; a focusing lens that focuses the dark beam onto particles moving through the illuminating dark beam; and two detectors. One of the two detectors is positioned over each intensity lobe of the dark beam. The beam interacts with the particles and the detectors measure the interaction signal and the number of interactions per unit time. These measurements are then mapped using algorithms. This system produces higher sensitivity due to a lower particle diameter dependency of the interaction signal. It also allows higher particle concentration measurements as the shorter wavelengths minimize optical noise. 

About Particle Measuring Systems, Inc.

Particle Measuring Systems (PMS) specializes in viable and nonviable particle counters and particle counting solutions that measure and monitor contamination levels in clean and controlled environments. Particle Measuring Systems is part of Spectris plc, the expert in providing insight through precision measurement.

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