A New Particle Counter Using Nonimaging Optics and Real-Time Correlation Filter for Particle Detection

A new particle counter designed specifically for particle detection within clean gas in pipes is described. The new particle counter uses a laser diode as its light source and detects the scattered light at a 90 scattering angle. Nonimaging optics, including optical light pipes and light concentrators, are also used. The dimensions of all the optical elements were manufactured in a range of several millimeters. A real-time cross-correlation filter (CCF) was developed for reducing false counts. Two parallel sensing zones, each more than 32 mm2 in area, were installed perpendicularly to the gas flow. Using the new particle counter, scattered light signals are continuously detected by two independent detectors and processed by the real-time CCF without dead time. Tests with various particles in the micrometer size range show that the new particle counter has lower local dependence of scattered light signal than common particle counters and has fewer false counts.