3D locating and sizing of volumetric metal droplets with astigmatic dual-beam interferometric particle imaging at panoramic scattering angle

Abstract

This work goes insight into the feasibility of astigmatic dual-beam interferometric particle imaging (ADIPI) to enable the measurement of three-dimensional (3D) positions and sizes of spherical metal droplets at panoramic scattering angle. The ADIPI signal exists at arbitrary angle except the two laser beam axes, defined as backward scattering region, forward scattering region, and sideward scattering region according to the angle of light scattering. A generalized model for three types of scattering situation is derived and an algorithm based on the ellipse detection and two-dimensional (2D) Fourier transform is applied to locate the centroid of each pattern and extract the spatial frequency and the inclination angle of fringes. Experiments are designed and performed, showing that the results in both of the depth position and size measuring of the same droplets measured from different angles are essentially identical. The average deviation values of the depth positions both are 1% for forward-sideward situation and backward-sideward situation. For backward-forward situation, backward-sideward situation and forward-sideward situation, the average deviation values in size measuring are 6%, 13% and 9%, respectively. The flexibility of ADIPI, breaking the strict requirements for equipment arrangement, can be carried out over a wide range of angles, facilitating its great potential in metal droplet measurement.