Dual-sheet interferometric particle imaging for opaque particle size and 2D location measurement

Fast and high-accuracy measurement of particle size and location from a linear interferogram

In this paper, we propose, to the best of our knowledge, a novel method of simultaneously detecting and evaluating the location and size of particles from a compression particle interferogram. The 2D position of the particle can be determined with high accuracy, as evaluated by the unidirectional gradient-match with the conjoint to centroid method. The fast-Rife method provides sub-pixel accuracy and high speed for estimating the fringe frequency from the Fourier spectrum of a particle interferogram. The capability mentioned above is well verified using synthetic and experimental data. The computational load falls almost 50%, and the relative error of the measured particle diameter is less than 1.12% for homogeneous solutions of polystyrene spheres of 50 µm and 70 µm. The results demonstrate that the method presented here is considerably promising for its application to a high-density particle field, such as spray, in accurately measuring both the particle size and its location.

Improving particle detection and size estimation accuracy in digital in-line holography using autoregressive interpolation

The accuracy of particle detection and size estimation is limited by the physical size of the digital sensor used to record the hologram in a digital in-line holographic imaging system. In this paper, we propose to utilize the autoregressive (AR) interpolation of the hologram to increase pixel density and, effectively, the quality of hologram reconstruction. Simulation studies are conducted to evaluate the influence of AR interpolation of a hologram on the accuracy of detection and size estimation of single and multiple particles of varying sizes. A comparative study on the performance of different interpolation techniques indicates the advantage of the proposed AR hologram interpolation approach. An experimental result is provided to validate the suitability of the proposed algorithm in practical applications.

Astigmatic dual-beam interferometric particle imaging for metal droplet 3D position and size measurement

We propose astigmatic dual-beam interferometric particle imaging (ADIPI) to simultaneously measure the three-dimensional (3D) position and size of spherical metal droplets. A theoretical model reveals that the orientation and spacing of the ADIPI fringes generated from the two reflections propagating through an astigmatic imaging system relate to the depth position and size, respectively. Proof-of-concept experiments on micron-sized gallium droplets are performed, and the tilted fringes in elliptical patterns are observed in the ADIPI interferogram, confirming theoretical predictions. Droplet 3D position and size are determined with ADIPI, and the relative discrepancies are within 5% and 2% compared to those with a dual-view digital inline holography system, demonstrating the feasibility and high accuracy of ADIPI.