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Design and Validation of a Holographic Particle Counter.
Georg Brunnhofer1,2,3, Alexander Bergmann2, Andreas Klug3
1Photonic Systems, CTR Carinthian Tech Research AG, 9524 Villach/St. Magdalen, Austria.
Sensors (Basel, Switzerland)
|November 14, 2019
Summary
A novel holographic particle counter accurately detects and counts multiple micrometer-sized particles in three dimensions. This particle imaging unit (PIU) offers precise in-situ measurements and scalable solutions for various particle concentrations.
Area of Science:
- Aerosol science and technology
- Optical particle characterization
- Instrumentation and measurement
Background:
- Accurate particle counting is crucial for environmental monitoring, industrial hygiene, and inhalation studies.
- Existing methods, like Condensation Particle Counters (CPCs), face limitations in handling high particle concentrations due to coincidence effects.
- In-line holographic techniques offer potential for 3D particle detection and high-throughput analysis.
Purpose of the Study:
- To present and validate a concept for an in-line holographic particle counter.
- To demonstrate the capability of detecting and counting micrometer-sized particles in a 3D sampling volume.
- To compare the performance of the proposed particle imaging unit (PIU) with a commercial CPC.
Main Methods:
- Development of a particle imaging unit (PIU) utilizing in-line holography.
- Application of image processing techniques with a customized Hough transform (HT) for particle detection and counting.
- In-situ comparison of the PIU with a commercial TSI-3775 CPC, mounted on a Condensation Nucleus Monitor (CNM).
Main Results:
- The PIU successfully detects and counts multiple micrometer-sized particles simultaneously within its 3D sampling volume.
- The system demonstrates linear expandability and cascading options for handling higher particle densities (>30,000 particles/cm³).
- Coincidence effects at higher concentrations were analyzed, and two correction approaches were presented, showing analogy to CPC methods.
Conclusions:
- The presented in-line holographic particle counter concept provides a precise and scalable method for in-situ particle number concentration determination.
- The PIU technology shows promise for accurate particle counting across a wide range of concentrations, including challenging high-density scenarios.
- The developed coincidence correction methods enhance the reliability of holographic particle counting, aligning with established CPC techniques.
