Optical Particle Counter (OPC) Particle size distribution of aerosol particles are measured in the size range of 0.15 to 5.0 µm. Main components of OPC are a He-Ne laser and a photodiode detector. Light scattered by a particle within a laser cavity is a function of particle size. The instrument is supervised by Leibniz Institute for Tropospheric Research (IFT), Leipzig, Germany.

Front plate of the instrument OPC. The instrument is constructed as standard 19'' plug in unit for the CARIBIC container.