In-line holography with a frequency doubled Nd:YAG laser for particle size analysis

Abstract

An arrangement for determining the size distribution of small particles (e.g., droplets or bubbles) is presented. It consists of taking high speed holograms with a frequency doubled Nd:YAG laser, reconstructing the real image with an argon-ion laser, and a digital image processing system with a random access image dissector camera and two cascaded computers for filtering, segmentation, and higher recognition tasks. Results are presented for cavitation bubbles as test objects. It is shown that the quality of the holograms is sufficient for detecting bubbles with a diameter of <20 mum by digital image processing with the present configuration.

Nonintrusive Measurement of the Structure of Dense Sprays

“…In spray combustion applications, the imaging of density variations can allow the vapor trail from individual particles to be recorded and visualized. 65 Argon-ion lasers have sufficient coherence length to produce holograms (on the order of tens of centimeters) but, for the short pulses required for the analysis of high-speed flows, the energy/pulse is too small to expose holographic film. A second consideration facing an investigator, in addition to the optical configuration, is the type of illumination to use to form the holograms.…”

Feasibility of off-axis particle field holography and imaging with portions of cylindrical test sections

“…As seen in the figure, the refractive indices of the tube material and the fluid inside are i and fl2, respectively. The tube thickness(6) is d. Thus , ifthe radius of curvature of the inner tube surface is -R, then that of the outer one is -(R+ d). Suppose the recording plane is at the distance D' from the outer tube58 / OPTICAL ENGINEERING / January 1992 / Vol.…”