Mitigating atmospheric effects in high-resolution infra-red surveillance imagery with bispectral speckle imaging

Obtaining a high-resolution image of an object or scene from a long distance away can be very problematic, even with the best optical system. This is because atmospheric blurring and distortion will limit the resolution and contrast of high-resolution imaging systems with substantial sized apertures over horizontal and slant paths. Much of the horizontal and slant-path surveillance imagery we have previously collected and successfully enhanced has been collected at visible wavelengths where atmospheric effects are the strongest. Imaging at longer wavelengths has the benefit of seeing through obscurants or even at night, but even though the atmospheric effects are noticeably reduced, they are nevertheless present, especially near the ground. This paper will describe our recent work on enhanced infrared (IR) surveillance using bispectral speckle imaging. Bispectral speckle imaging in this context is an image postprocessing algorithm that aims to solve the atmospheric blurring and distortion problem of imaging through horizontal or slant path turbulence. A review of the algorithm as well as descriptions of the IR camera and optical systems used in our data collections will be given. Examples of horizontal and slant-path imagery before and after speckle processing will also be presented to demonstrate the resolution improvement gained by the processing. Comparisons of IR imagery to visible wavelength imagery of the same target under the same conditions will be shown to demonstrate the tradeoffs of going to longer wavelengths