Imaging through the atmosphere is an important technology area, with applications in fields such as astronomy and remote sensing. For optimal results, many facets of signal collection and recovery must be understood. These facets include understanding relevant atmospheric effects, optimizing the signal collection system, and effectively processing the collected signals to obtain the desired imagery. Many different types of radiation can be used to obtain images through the atmosphere, including microwave, infrared, and optical. This radiation can be supplied by the object or natural sources (passive illumination), or it can be provided by the user (active illumination). This focus issue contains a number of invited papers describing imaging work being accomplished in the Advanced Optics and Imaging Division of the Air Force Research Laboratory, formerly the Optical Sensing Division of the Air Force Phillips Laboratory. These papers assume that optical or infrared radiation is being used, either actively or passively.
McMackin, Hugo, Pierson, and Truman describe an optical tomography system which can be used to characterize dynamic transparent media such as air flow. The authors emphasize the high speed capability of their system, demonstrated using air flow from a heated-air jet.
Landesman, Kindilien, Pierson, Matson, and Mosley analyze the effects of cirrus clouds upon coherent laser illumination used for an active imaging experiment. They suggest that the interaction of such radiation with cirrus clouds can result in a deterministic component in the detected return due to the clouds, which may possibly be exploited for improved imagery.
Marker and Jenkins look at how low-weight optics, such as space-based inflatable optics, can be actively controlled to obtain the desired surface shape. Their approach to shape modification uses boundary displacements.
McMackin, Voelz, and Fetrow present a multiple wavelength interferometry technique for characterizing highly-aberrated optical surfaces. Their approach combines multiple wavelength interferometry with a heterodyne array sensing technique, which can provide rapid wavefront measurements with high spatial and phase resolution.
Dayton, Sandven, Gonglewski, Browne, Rogers, and McDermott describe how a spatial light modulator can be used as a deformable mirror to obtain high-precision wavefront control. Their technique employs a Shack-Hartmann wavefront sensor along with a zonal control algorithm.
Tyler and Matson analyze how the known support of an object can be used to decrease noise inside the object’s support when the noise is not wide-sense-stationary (WSS) in the Fourier domain. Previous work had shown that there are serious limits to the removal of WSS noise; however, these limits are removed when the noise is not WSS.
Schulz, Stribling, and Miller present their approach to multiframe blind deconvolution which is implemented using an iterative algorithm based upon the expectation-maximization procedure. They show results from their algorithm using images of the Hubble Space Telescope collected with a ground-based telescope.
All of these papers were invited for this focus issue, and I am indebted to the authors for the time and effort they have spent to contribute such high-quality results.