Processing of digital holograms for size measurements of microparticlese

Abstract

Digital holography has been reported as an effective tool for particle analysis. Other image-based techniques have small depth of focus allowing only 2D analysis at microscopic level. On the other hand, digital holography offers the ability to study volume samples from a single recording as reconstructions at different depths can be obtained. This paper focuses on the processing of the digital hologram that follows its recording in order to obtain particle size. We present a stepwise processing procedure with discussion on aspects such as reconstruction, background correction, segmentation, focusing, magnification and particles' feature extraction. Solutions to common obstacles faced during particle analysis which include ways to obtain fixed size reconstructions, automatically determine the threshold value, calculate magnification, and locate particles' depth position using effective focusing metrics are highlighted. Real holograms of microparticles are used to illustrate and explain the different stages of the procedure. Experimental results show that the proposed algorithm can effectively extract particle size information from recorded digital holograms.

On-line digital holographic measurement of size and shape of microparticles for crystallization processes

“…The mean particle size identified from the holographic microscopy was 81.1 µm and the standard deviation was 14.61 µm, which showed a good agreement with the particle size distribution which was measured using a scanning electron microscopy (SEM). 16 Fig. 4 (b) shows the ALD of ceramic beads.…”

“…16 For the sake of completeness it is briefly described here. The hologram is reconstructed at several depths covering the volume to be examined.…”

“…The recoded holograms were processed following the procedure described in Section 2.2, whose details can be found elsewhere. 16 For the reconstruction of each hologram, a step size of 50 µm covering a volume of depth size of 3 mm was used. Fig.…”

Three dimensional digital holographic profiling of micro-fibers

“…In the case of spherical particles, several localization algorithms have been developed [1,5]. A few studies have dealt with the development of localization algorithms for fibers.…”

On-line monitoring of particulate processes using digital holography

“…Furthermore, imperfections such as non-uniform illumination of the hologram lowers the performance of thresholdbased segmentation. Some additional details regarding the drawbacks of threshold-based segmentation are given elsewhere [122].…”