Study On Glare Points Measurement Method Of Particle Field

Particle field measurements play an important role in scientific research, engineering and other fields. Interferometric particle imaging (IPI) technique is a relatively new particle measurement technique. Scattering light of particles form fringe on defocus image and glare points on focus image. Particle size is measured by fringe frequency of defocus image or two glare point’s distance of focus image. Particle velocity measure can be achieved by PTV/PIV technique and measurement accuracy depends on image technology. This paper studied the basic theory of IPI technique and image processing algrorithm of focus image. The main works as follows has been done:1. The basic principle of IPI with two lights illumination is studied and the effects of experimental system parameters to measurable particle range, accuracy are analysised.2. An algorithm of identify particle center based on template matching has been proposed. Particle field of different size and different densities has been simulated and the error of extracting the space of two glare points has been analysised.3. The relations between overlapped coefficient, recognition ratio and center location of focus image have been analyzed. The centers of two particles overlaped in±45°direction can be recognized extractly by the image processing algrorithm at γ≤77.65%, that is Ad=7(?)2pix. On the direction of+45°and-45°, when γ≤50.18%and γ≤53.56%, that is Δd=29(?)2pix and Δd=26(?)2pix respectively, fringe frequency can be recognized accurately.4. The IPI system of two lights illumination is set up. Standard particle size of15.3μm,25μm and45μm are measured respectively. The measurement results:for the fringe pattern, the particle size are17.2±1.1μm,26.2±0.7μm and44.1±0.9μm respectively. The relative errors are12.4%,4.8%and2.0%respectively. For the glare points pattern, the particle size are17.3±0.5μm,26.3±0.6μm and46.0±.6μm respectively. The relative errors are13.1%,5.2%and2.2%respectively.5. The velocity of15.3μm particles based on fringe mode and glare points mode are measured by PTV technique and obtain the2D velocity vector of particles.