Structured illumination and image enhancement of three-dimensional and moving objects at a distance via incoherent Fourier ptychography.

We experimentally apply incoherent Fourier ptychography to enhance the resolution of recorded images by projecting known, uncorrelated, random patterns at high speed onto 3D moving and distant objects. We find that the resolution enhancement factor can be greater than 2, depending on the projection and camera optics.

Multi-spectral SWIR lidar for imaging and spectral discrimination through partial obscurations.

We have developed a multi-spectral SWIR lidar system capable of measuring simultaneous spatial-spectral information for imaging and spectral discrimination through partial obscurations. We employ objects in the presence and absence of a series of obscurants to evaluate the capability of the system in classifying the objects of interest based on spectral and range information. We employ a principal component analysis-based algorithm in classifying the objects and quantifying the accuracy of detection under various obscured scenarios. The merits of multi-spectral lidar over hyperspectral imaging are highlighted for target identification in the presence of obscurants.

Wide-field interferometric measurement of a nonstationary complex coherence function.

Spatial coherence function (SCF) is a complex function of two spatial coordinates that, in general, carries more information than the bare intensity distribution. A fast and quantitatively accurate measurement of the SCF is extremely important for a range of applications in optical sensing and imaging. Here, we demonstrate an efficient two-step procedure for measuring the full-field complex coherence function. The measurement relies on an optimized design of a wavefront shearing interferometer capable of characterizing spatially inhomogeneous fields over an extended angular domain. The measurement precision is confirmed by the excellent agreement with a numerical estimation based on Fresnel calculations. We demonstrate that the sensitivity and the measurement range afforded by our instrument permits us to reliably describe the differences in the complex coherence functions that are due to subtle modifications in the shape, position, and orientation of radiation sources.

Babinet's principle for mutual intensity.

In classical diffraction theory, Babinet's principle relates the electromagnetic fields produced by complementary sources. This theorem was always formulated for single-point quantities, both intensities or field amplitudes, in conditions where the full spatial coherence is implicitly assumed. However, electromagnetic fields are, in general, partially coherent, and their spatial properties are described in terms of two-point field-field correlation functions. In this case, a generalized Babinet's principle can be derived that applies to the spatial coherence functions. We present both the derivation and the experimental demonstration of this generalized Babinet theorem.