Retrieval of diffraction-limited images from below the threshold of recognition by superdirective data processing

The resolution of long-wavelength imaging systems is normally limited by the effective recording-aperture dimension, and may preclude target recognition. It is shown that, for imaging systems in which complex field values are recorded, the aperture can be effectively extrapolated by a superdirective weighting function, thereby restoring essential features to a severely diffraction-limited image. Limitations to image enhancement arising from spatial noise in the object plane are discussed.