Linear interferometric image processing for analysis of a particle in a volume

Abstract

A method of extracting the number of fringes/fringe spacing of compression interferogram based on a wavelet-matched filter and Fourier transform technique is proposed, and sub-pixel accuracy of the extracted frequency is achieved by the modified Rife algorithm. Both numerical simulation and experimental measurement are carried out to verify the performance of the method. The measurement uncertainty is ±1.118 µm and the absolute error is 1.873 µm for standard particles of diameter 45 µm. The research results show that the algorithm presented in this paper is feasible, and is promising for application to a high-density spray field.

Measuring droplet size distributions from overlapping interferometric particle images

“…Next, we find the spatial fringe frequency through another Fourier transform, the result of which provides seeds for a least-squares fit of the fringe profile. We emphasize that the ingredients of this procedure are not new-both the Fourier- 11 and the wavelet transform have been discussed before 6,7 -but the combination, and especially the hierarchical approach to find the best particle disks is new.…”

“…In contrast, our only selection criterion is a recognizable local maximum of the convolution between the image and the used disk-like kernel. In a recent paper, 7 fringe frequencies were determined precisely using Fourier-and interpolation techniques.…”

Measurement of irregular particle size from the reconstructed shape images

“…However, interferometric particle imaging (IPI) [5] has the advantages of * Author to whom any correspondence should be addressed. wide measurement range, high precision, non-contact measurement and rapid measurement, which is extensively applied to the measurement of irregular particles [7][8][9][10][11][12][13][14]. Researchers have conducted considerable work on the basis of this technique.…”