Synthetic Aperture Scatter Imaging

Abstract

Diffraction limits the minimum resolvable feature on remotely observed targets to $\lambda R_{c}/A_{c}$, where $\lambda$ is the operating wavelength, $R_{c}$ is the range to the target and $A_{c}$ is the diameter of the observing aperture. Resolution is often further reduced by scatter or turbulence. Here we show that analysis of scattered coherent illumination can be used to achieve resolution proportional to $\lambda R_{s}/A_{s}$, where $R_{s}$ is the range between the scatterer and the target and $A_{s}$ is the diameter of the observed scatter. Theoretical analysis suggests that this approach can yield resolution up to 1000× better than the diffraction limit. We present laboratory results demonstrating $>30\times$ improvement over direct observation. In field experiments, we use a 23.5 cm aperture telescope at 100 m to resolve 27.78 $\mu$m features, improving on diffraction limited resolution by $>10\times$. The combination of lab and field results demonstrates the potential of scatter analysis to achieve multiple order of magnitude improvements in resolution in applications spanning microscopy and remote sensing.

Keywords

• Coherent imaging
• non-line-of-sight imaging
• phase retrieval
• super resolution