Four-view single-camera plenoptic 3.0 imager for three-dimensional Lagrangian particle tracking in an oscillatory laminar boundary layer

Abstract

We show a novel plenoptic camera architecture and demonstrate its ability to perform three-dimensional three-component velocimetry using standard multi-camera processing techniques. The field of view of the imager is approximately \(10~\text {mm}\times 7~\text {mm}\times 3\,\text {mm}\). The architecture needs only a custom lens assembly with no modification to the camera body, which allows the use of any camera with an appropriate sensor size. This plenoptic configuration directly creates multiple views of a scene side by side on the camera sensor, which are then separated and treated as if they originated from independent cameras. Standard calibration techniques are implemented to create 3D to 2D correspondence on images to determine 3D scene information. 3D velocity fields are reconstructed with the “shake-the-box” implementation of Lagrangian particle tracking. Results are validated with an axially oscillating cylinder in a refractive-index-matched experiment. The flow is the axisymmetric equivalent of Stokes second problem for which an analytical solution is known. The boundary layer is \(1.24~\textrm{mm}\) with large accelerations and velocity gradients, which serve as a strong test case for the instrument.