DIFFRACTION-LIMITED IMAGING WITH PARTIALLY REDUNDANT MASKS .1. INFRARED IMAGING OF BRIGHT OBJECTS

The utility of partially redundant pupil geometries has been studied in the context of near-infrared speckle imaging with ground-based telescopes. Using both numerical simulations and experimental data collected with a 4-m-class telescope, we find that the decrease in redundancy resulting from apodizing the telescope pupil results in an enhancement of the quality of reconstructed images at high light levels. This improvement in imaging fidelity is particularly valuable when short-term variations in the statistics of the atmosphere make the seeing calibration of speckle interferograms difficult. However, the use of an apodizing mask necessarily restricts the faintest source that can be imaged, leading to a loss in sensitivity of one to two magnitudes. For many of the brighter near-infrared astrophysical sources in the sky that have been the subject of previous speckle-imaging studies, the use of a partially redundant pupil is expected to enhance the fidelity of the imaging procedure considerably.