Materials, Photonic Devices, and Sensors

Selectivity and balance of spatial filtering velocimetry of objective speckles for measuring out-of-plane motion

[+] Author Affiliations
Michael Linde Jakobsen, Steen Grüner Hanson

DTU Fotonik, Technical University of Denmark, Department of Photonics Engineering, P.O. Box 49, Roskilde DK-4000, Denmark

Hal T. Yura

Electronics and Photonics Laboratory, The Aerospace Corporation, P.O. Box 92957, Los Angeles, California 90009, United States

Opt. Eng. 54(4), 047103 (Apr 09, 2015). doi:10.1117/1.OE.54.4.047103
History: Received November 5, 2014; Accepted March 17, 2015
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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.

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© 2015 Society of Photo-Optical Instrumentation Engineers

Citation

Michael Linde Jakobsen ; Hal T. Yura and Steen Grüner Hanson
"Selectivity and balance of spatial filtering velocimetry of objective speckles for measuring out-of-plane motion", Opt. Eng. 54(4), 047103 (Apr 09, 2015). ; http://dx.doi.org/10.1117/1.OE.54.4.047103


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