FMCW Differential Synthetic Aperture Ladar for Turbulence Mitigation

Synthetic Aperture (SA) imaging, including holographic aperture ladar (HAL), synthetic aperture ladar (SAL), and combinations thereof; are promising solutions for long range imaging applications. One of the major difficulties with real-world SA imaging is coherently processing the image information in the presence of atmospheric turbulence. Differential SAL imaging was proposed and patented in 2005 as a technique to reduce the sensitivity of synthetic aperture imaging ladar to line-of-sight motion errors and shown to reduce sensitivity to dynamic turbulence near the target. We will present experimental laboratory demonstrations of high range resolution DSAL with comparisons of performance to standard SAL processing in the presence of localized dynamic turbulence. Our DSAL receiver is based on imaging the receive aperture and LO onto quad-cell detectors that measure the ladar signal in each quadrant of the aperture separately. We will also discuss how differential techniques can mitigate atmospheric turbulence with other SA imaging techniques.