Abstract
An in-line holographic particle counter concept is presented and validated where multiple micrometer sized particles are detected in a three dimensional sampling volume, all at once. The proposed Particle Imaging Unit is capable of detecting holograms of particles which sizes are in the lower m- range. The detection and counting principle is based on common image processing techniques using a customized Hough Transform with a result directly relating to the particle number concentration in the recorded sampling volume. The proposed counting unit is mounted ontop of a Condensation Nucleus Magnifier for comparison with a commercial TSI-3775 Condensation Particle Counter (CPC). The concept does not only allow for a precise in-situ determination of low particle number concentrations but also enables easy upscaling to higher particle densities (e.g., ) through its linear expandability and option of cascading. The impact of coincidence at higher particle densities is shown and two coincidence correction approaches are presented where, at last, its analogy to the coincidence correction methods used in state-of-the-art CPCs is identified.
Highlights
A major topic in aerosol measurement is the detection of aerosol Particle Number (PN)
Aerosol Electrometers are gaining more and more relevance for measuring high particle number concentrations, Optical Particle Counters (OPCs) still represent the most universal instruments to cope with low particle numbers
As standard optical microscopy is most often not eligible for commercial reasons, particles are counted after they are grown to micron size using standard instruments, such as Condensation Particle Counters (CPCs)
Summary
A major topic in aerosol measurement is the detection of aerosol Particle Number (PN). Aerosol Electrometers are gaining more and more relevance for measuring high particle number concentrations, Optical Particle Counters (OPCs) still represent the most universal instruments to cope with low particle numbers. Light scattering provides a direct measure of PN, particle size distribution and particle shape [1,2,3,4]. It requires the magnification of nanoparticles to make them optically detectable. As standard optical microscopy is most often not eligible for commercial reasons, particles are counted after they are grown to micron size using standard instruments, such as Condensation Particle Counters (CPCs)
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