Conference paper Open Access

Measurements of bubble size distributions with an optical technique based on depth from focus

Geißler, Peter; Jähne, Bernd

An optical sensor for bubble size measurements is presented. It is based on
the combination of light blocking visualization and depth from focus techniques
and allows for the measurement of single bubbles. The degree of blur
in the images of single bubbles is used to compute the distance from focal
plane and thus to determine a virtual measuring volume that is increasing
with bubble size. The image sequences are evaluated using digital image
processing to calculate bubble size distributions. Experiments performed
in the linear wind/wave facility of Delft Hydraulics are presented. For different
wind speed conditions and depths bubble spectra in fresh water have
been measured.

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