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Optical Methods for Data Processing in Heat and Fluid Flow by James Buick, John Cosgrove, Clive Greated

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7

Development of Full-volume Digital Holography for Particle Measurement

S Murata and N Yasuda

Abstract

This Chapter presents a digital method for detecting the position of small particles distributed in three-dimensional space from in-line hologram patterns. The detection is carried out by numerically reconstructing the real image of the particles from observed hologram patterns. In the present method that is called full volume digital holography, two-dimensional real images are reconstructed at a constant small interval in depth to obtain the three-dimensional light intensity distribution of the real images. Three different types of template are tested for searching local minimums in the three-dimensional light intensity distribution which express particle positions in three-dimensional space. The measurement accuracy of the present method is examined in numerical simulation and in experiment, and it is found that the template of circular cylinder gives better results than the other templates and the RMS error is about 1.8 mm using a binary template.

Notation

d depth of a tracer particle
d′ detected depth of a tracer particle
D diameter of template
gF a Gaussian function
hz light amplitude on image plane
H height and width of template
Id light intensity on hologram plane (Transparency function)
Iz light intensity on image plane
j imaginary unit
x, y Cartesian co-ordinates on hologram plane
xz, yz Cartesian co-ordinates on image plane
x0, y0, z0 Cartesian ...

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