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Optical Engineering

Selectivity and balance of spatial filtering velocimetry of objective speckles for measuring out-of-plane motion
Author(s): Michael Linde Jakobsen; Hal T. Yura; Steen Grüner Hanson
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Paper Abstract

We probe the dynamics of objective laser speckles as the axial distance between the object and the observation plane changes. With the purpose of measuring out-of-plane motion in real time, we apply optical spatial filtering velocimetry to the speckle dynamics. To achieve this, a rotationally symmetric spatial filter is designed. The spatial filter converts the speckle dynamics into a photocurrent with a quasi-sinusoidal response to the out-of-plane motion. Our contribution presents the technology, discusses the selectivity of the spatial filter and proposes two solutions to balance phase-stepped photocurrents. Specifically, we discuss how the selectivity of the spatial filter with regard to radial speckle motion is influenced by a concurrent in-plane speckle motion. The spatial filter is emulated with a CCD camera and is tested on speckle acquisitions obtained from a controlled setup. Experiments with the emulated filters illustrate the performance and potential applications of the technology.

Paper Details

Date Published: 9 April 2015
PDF: 9 pages
Opt. Eng. 54(4) 047103 doi: 10.1117/1.OE.54.4.047103
Published in: Optical Engineering Volume 54, Issue 4
Show Author Affiliations
Michael Linde Jakobsen, DTU Fotonik (Denmark)
Hal T. Yura, The Aerospace Corp. (United States)
Steen Grüner Hanson, DTU Fotonik (Denmark)

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