Publications

Abstract not provided.

The design, construction, and testing of a high-magnification, long working-distance plenoptic camera is reported. A plenoptic camera uses a microlens array to enable resolution of the spatial and angular information of the incoming light field. Instantaneous images can be numerically refocused and perspective shifted in post-processing to enable threedimensional (3D) resolution of a scene. Prior to this work, most applications of plenoptic imaging were limited to relatively low magnifications (1× or less) or small working distances. Here, a unique system is developed with enables 5× magnification at a working distance of over a quarter meter. Experimental results demonstrate ~25 µm spatial resolution with 3D imaging capabilities. This technology is demonstrated for 3D imaging of the shock structure in a underexpanded, Mach 3.3 free air jet.

Plenoptic background oriented schlieren imaging has recently been introduced as a single-camera technique used to observe three-dimensional density gradients in a flow field. With the ability to generate focused BOS images, the signature of density gradients produced at different depth locations can be distinguished from one another. Two experiments demonstrate the capabilities of this technique. The first experiment visualized the rising plumes produced from two simple flames placed at different depths in a low magnification configuration. The second experiment used a high magnification configuration with long working distance to visualize shock waves in a 6.35 millimeter diameter underexpanded jet. These experiments demonstrate plenoptic BOS as a simple and convenient three-dimensional visualization technique that can be applied in facilities with limited optical access.

We report digital inline holography (DIH) provides instantaneous three-dimensional (3D) measurements of diffracting objects; however, phase disturbances in the beam path can distort the imaging. In this Letter, a phase conjugate digital inline holography (PCDIH) configuration is proposed for removal of phase disturbances. Brillouin-enhanced four-wave mixing produces a phase conjugate signal that back propagates along the DIH beam path. Finally, the results demonstrate the removal of distortions caused by gas-phase shocks to recover 3D images of diffracting objects.

Abstract not provided.