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.
Original language | English |
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Article number | 047103 |
Journal | Optical Engineering |
Volume | 54 |
Issue number | 4 |
Number of pages | 10 |
ISSN | 0091-3286 |
DOIs | |
Publication status | Published - 2015 |
Keywords
- 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