Reconstruction of aperture-synthesis images from LBT LINC-NIRVANA data using the Richardson-Lucy and space-variant Building Block method

We present a new method, the regularized and space-variant Building Block method, which is able to reconstruct diffraction-limited aperturesynthesis images from Large Binocular Telescope (LBT) LINC-NIRVANA data. Images with the diffraction-limited resolution of a 22.8 m single-dish telescope can be derived if raw images are taken at several different hour angles. We simulated computer-generated and laboratory LBT interferograms that are similar to the data which can be obtained with the LINC-NIRVANA beam combiner instrument. From the simulated data, diffraction-limited images were reconstructed with the regularized Building Block method, which is an extension of the Building Block method (Hofmann & Weigelt 1993, A&A, 278, 328). We compare the Building Block reconstructions to images obtained with the Richardson-Lucy (RL) method (Richardson 1972, J. Opt. Soc. Am., 62, 55; Lucy 1974, AJ, 79, 745) and the Ordered Subsets Expectation Maximization (OSEM) method (Hudson & Larkin 1994, IEEE Trans. Med. Imag., 13, 601; Bertero & Boccacci 2000, A&AS, 144, 181). Our image reconstruction studies were performed with computer-simulated J-band and laboratory H-band raw data of a galaxy with simulated total magnitudes of J = 16m to 18m and H = 16m to 19m, respectively. One of the faintest structures in the images has a brightness of J ∼ 25m. The simulated reference stars within the isoplanatic patch have magnitudes of J = 20m−21m and H = 19m. All three methods are able to reconstruct diffraction-limited images with almost the same quality. Furthermore, raw data with space-variant point spread functions were simulated, and diffraction-limited images were reconstructed using the space-variant version of the Building Block method.