Particle analysis based on light extinction method illuminated by a divergent beam

A novel model based on the Monte Carlo principle was put forward to study the phenomenon of particle extinction spectrum under the condition of divergent incident beams and analyze the deviation during particle size inversion. Both the simulation results and experimental results show that the light extinction effect enhances obviously with the increase of divergence angle, accompanied by the distortion of extinction spectrum itself, which is closely related to particle size and optical wavelength. When the divergence angle is up to 20°, the observed relative error during the retrieval of particle size can reach 12.8%, by comparing those obtained by the Lamber-Beer law for particle to the nominal diameter of 0.8 μm. Accordingly, an improved inversion technique was studied, which yielded the particle size measurement error <2% for particles of 0.2 μm, 0.8 μm and 2.88 μm in nominal size.