Synthetic-aperture imaging laser radar: laboratory demonstration and signal processing

• Published in: Applied optics (2004) 2005-12, Vol.44 (35), p.7621-7629
• Main Authors: Beck, Steven M, Buck, Joseph R, Buell, Walter F, Dickinson, Richard P, Kozlowski, David A, Marechal, Nicholas J, Wright, Timothy J
• Format: Article
• Language: English
• ISSN: 1559-128X
• DOI: 10.1364/AO.44.007621

The spatial resolution of a conventional imaging laser radar system is constrained by the diffraction limit of the telescope's aperture. We investigate a technique known as synthetic-aperture imaging laser radar (SAIL), which employs aperture synthesis with coherent laser radar to overcome the diffraction limit and achieve fine-resolution, long-range, two-dimensional imaging with modest aperture diameters. We detail our laboratory-scale SAIL testbed, digital signal-processing techniques, and image results. In particular, we report what we believe to be the first optical synthetic-aperture image of a fixed, diffusely scattering target with a moving aperture. A number of fine-resolution, well-focused SAIL images are shown, including both retroreflecting and diffuse scattering targets, with a comparison of resolution between real-aperture imaging and synthetic-aperture imaging. A general digital signal-processing solution to the laser waveform instability problem is described and demonstrated, involving both new algorithms and hardware elements. These algorithms are primarily data driven, without a priori knowledge of waveform and sensor position, representing a crucial step in developing a robust imaging system.