Sensitivity to piston and adaptive optics errors with the

F. Patru, S. Esposito, A. Puglisi, A. Riccardi, E. Pinna, C. Arcidiacono, J. Hill, P. Hinz

Research output: Contribution to journalConference articlepeer-review


On-sky adaptive optics wavefront screens have been used and random optical path fluctuations-differential pistons-have been included in numerical simulations for the LBTI. The interferometric Strehl which can be achieved by the LBTI using two FLAO is close to the AO Strehl provided by a FLAO standalone, as long as other sources of aberrations can be mitigated (Fig. 1). The imaging performance of the LBTI is thus fundamentally limited by the AOcorrection level. The tip-tilts induced by both AO systems onto each sub-aperture produce differential tip-tilts of the sub-beams and differential shifts of the sub-images (Fig. 2, 4, 5), so that the diffraction envelopes do not overlap properly and the beams do not fully interfere coherently. However, for piston fluctuations, the fringes move back and forth within the Airy disk (Fig. 3, 4, 5), reducing the fringe contrast for a long exposure, but not for a short one. A snapshot retains high angular resolution information by freezing the fringes. Few criteria have been evaluated as a merit function (Fig. 6, 7) to characterise the Point Spread Function (PSF) and the Optical Transfer Function (OTF). The R23 quantity is more sensitive than the interferometric Strehl to the contrast attenuation induced by the shift of the fringes in a long exposure (image blurring). The visibility should not be used as a merit function, but as a criterium for science applications. The contrast in the PSF enables to highlight two regimes depending on the location in the diffractive pattern, either in a sidelobe (low contrast) or in a valley (high contrast). The FWHM of the central peak of the MTF may be used to sense the low order aberrations from each AO systems. For instance, large tip-tilts produce fringes in the central peak affecting the FWHM in real-time.

Original languageEnglish (US)
Article number1001505
JournalProceedings of SPIE - The International Society for Optical Engineering
StatePublished - Jul 29 2018
Externally publishedYes
EventSPIE Astronomical Telescopes and Instrumentation 2016 - Edinburgh, United Kingdom
Duration: Jun 26 2016Jul 1 2016

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering


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