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

Michael Linde Jakobsen, Hal T. Yura, Steen Grüner Hanson

    Research output: Contribution to journalJournal articleResearchpeer-review


    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.
    Original languageEnglish
    Article number047103
    JournalOptical Engineering
    Issue number4
    Number of pages10
    Publication statusPublished - 2015


    • spatial filtering velocimetry
    • speckle phenomena
    • velocity sensor
    • Beamforming
    • CCD cameras
    • Dynamics
    • Velocimeters
    • Velocity measurement
    • Axial distance
    • Observation planes
    • Out-of-plane motion
    • Spatial filtering velocimetry
    • Spatial filters
    • Speckle dynamics
    • Speckle phenomenon
    • Velocity sensor
    • Speckle


    Dive into the research topics of 'Selectivity and balance of spatial filtering velocimetry of objective speckles for measuring out-of-plane motion'. Together they form a unique fingerprint.

    Cite this