This paper describes two superresolution coherent imaging techniques, which both use a diffraction grating to direct high spatial frequency information that would otherwise be lost through the imaging system pupil. The techniques employ digital holography to measure the optical field in the image plane and rely on capturing multiple holograms with the illumination condition altered between exposures. In one case, we used linear signal processing to separate aliased spectral regions, while in the second case we directly measured spectral regions without aliasing. In both cases, we stitched together higher-bandwidth synthetic aperture spectra and used them to reconstruct superresolution images. Our experimental results validated the approaches, demonstrating a resolution gain factor of approximately 2.5. (C) 2016 Optical Society of America
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