Accurate measurement of out-of-plane particle displacement from the cross correlation of sequential digital in-line holograms

Abstract

A new method to quantify three-dimensional particle fields using digital in-line holography is presented. From sequentially recorded holograms, the maximum cross correlation of edge sharpness within local particle windows yields an accurate measurement of particle displacements. Experiments demonstrate out-of-plane displacement uncertainty of approximately 0.15 mean particle diameters, which is roughly an order-of-magnitude improvement compared with alternative methods. Application to shotgun pellets demonstrates robustness despite experimental noise.

Developments in digital in-line holography enable validated measurement of 3D particle field dynamics

“…By simultaneously searching throughout z in both holograms and calculating the cross-correlation of refocused particle images, an accurate measure of 3D particle positions and displacements can be obtained from the conditions where the cross-correlation coefficient maximizes. Details of this method are published in an Optics Letters article [13]. Using the same experimental data of quasi-stationary particles reported in § 2, measured displacements of z = 1.996 ± 0.072 mm (mean ± standard deviation) are found using the cross-correlation method.…”

“…Consequently, it is possible to accurately measure the size and 3C velocity of the pellets in the shotgun blast, as shown in Figure 6. Again, for full details on these results, the reader is referred to Guildenbecher et al [13]. …”

“…This report summarizes developments in DIH obtained during the course of a Laboratory Directed Research and Development (LDRD) project at Sandia National Laboratories spanning the January 2011 to December 2013 timeframe. Following a brief explanation of the underlying principles and challenges, specific developments are presented with reference to a number of published works [3][4][5][6][7][8][9][10][11][12][13]. Figure 2 shows the basic experimental configuration of DIH.…”

Direct particle depth displacement measurement in DHPTV using spatial correlation of focus metric curves

“…Holography, as a real 3D imaging technique, is capable of reviving the 3D information of the tracer particles, and thus has been widely applied to particle field diagnostics [2,3]. Besides the size and 3D position measurement [4][5][6], digital holography has also been extended to measure the 3D velocity in a manner of particle tracking/image velocimetry (PTV/ PIV) [7][8][9][10][11][12][13][15][16][17][18]. Digital holographic PTV (DHPTV) shows great potential in measurements of 3D velocity field.…”

“…In DHPTV, we usually record a pair [8,12,13,16,17] (or a series [10,11]) of holograms or a hologram with multi-exposures [14,15], and then reconstruct the 3D optical particle fields to retrieve the 3D velocity field. The existing algorithms for 3D velocity calculation fall into two categories: cross-correlation (3D [9] or 2D [17]) and tracking particle one by one [7,8,[10][11][12][13][15][16][17].…”