On the Impact of Subaperture Sampling for Multispectral Scalar Field Measurements

Abstract

The novel 3D imaging and reconstruction capabilities of plenoptic cameras are extended for use with continuous scalar fields relevant to reacting flows. This work leverages the abundance of perspective views in a plenoptic camera with the insertion of multiple filters at the aperture plane. The aperture is divided into seven regions using off-the-shelf components, enabling the simultaneous capture of up to seven different user-selected spectra with minimal detriment to reconstruction quality. Since the accuracy of reconstructed features is known to scale with the available angular information, several filter configurations are proposed to maintain the maximum parallax. Three phantoms inspired by jet plumes are simulated onto an array of plenoptic cameras and reconstructed using ASART+TV with a variety of filter configurations. Some systematic challenges related to the non-uniform distribution of views are observed and discussed. Increasing the number of simultaneously acquired spectra is shown to incur a small detriment to the accuracy of reconstruction, but the overall loss in quality is significantly less than the gain in spectral information.

Perspective on the development and application of light-field cameras in flow diagnostics

“…The use of plenoptic cameras for 3D scalar-field measurements involves reconstruction of a 3D luminescent field such as flame or fluorescing flow [77][78][79][80][81][82], and in some instances, further specialization into simultaneous multi-spectral measurements by installing color filters within the plenoptic camera (see next section) [79,80], or derivation of physical quantities such as 3D flame temperature-fields by assuming proportionality between luminescence and temperature [81,82].…”

“…Ongoing works in this field continue to explore variations of algorithms to improve reconstruction, including adaptive simultaneous algebraic reconstruction technique (ASART) with total variation regularization [79], dynamic masking [79], and potential incorporation of prior knowledge among others. In our opinion, plenoptic cameras may not maximally demonstrate its potential in single-physics 3D scalar-field measurement, where large perspective-view redundancy does not equate to significant quality improvement.…”