Agile beam/wavefront control for sub-aperture-based imaging systems

ABSTRACT: Boulder Nonlinear Systems recently developed and delivered a beam scanner that non-mechanically steers a monochromatic, 5-cm beam over an 80a x 80a field of regard (FOR) with sub-milliradian resolution. This prototype uses a transmissive, wide-angle stepper (coarse steering unit), which is very compact and easily inserts into conformal, sub-aperture assemblies. To provide high resolution, the system incorporates a reflective, small-aperture, fine-angle beam steerer, which acts to fill in between the wide-angle steps. This fine angle unit and its associated beam expander quadruple the size and complexity of the beam control assembly, making it more difficult to use in fast optical systems. A solution is to develop a thin, large-aperture, transmissive unit, which works directly in-line with the coarse steering unit, to provide fine angle steering and high-resolution wavefront control. Also, we propose using wavelength-independent phase control for both the fine and coarse steering elements, which allows broadband operation using achromatic Fourier transform (AFT) techniques. This project capitalizes on the University of Daytons research in meta materials to make the AFT approach practical for compact assemblies. Through this effort, compact, conformal, sub-aperture imaging systems, which panchromatically operate over a wide FOR (b45a) with ~109 instantaneous fields of view, become realizable. BENEFIT: The ability to provide non-mechanical, wide-angle, beam control for conformal optical apertures is needed where reducing the size, weight and power consumption of the system is crucial and operation over a large field of regard is mission critical. Some of these applications are free space optical communications, remote sensing and weapon guidance. Non-mechanical systems have the potential to be more accurate, smaller, lighter and less expensive than systems that use gimbals to position the beam. Future deployment of optical systems in small or high performance aircraft will eventually require these attributes to prevent platform integration from affecting aircraft performance or disturbing the air stream.