Tilt Estimation in Moderate-to-Strong Scintillation

• Published in: Applied optics (2004) 2001-06, Vol.40 (18), p.2966-2972
• Main Authors: Burl, J B, Roggemann, M C, Welsh, B
• Format: Article
• Language: English
• ISSN: 1559-128X
• DOI: 10.1364/AO.40.002966

Adaptive optics systems are being applied in ever more challenging environments, for example, the projection of lasers over long horizontal paths through the atmosphere. These long atmospheric paths corrupt the signal received from the beacon and typically yield highly scintillated received wave fronts. Tilt estimation for controlling the fast steering mirror in these systems is complicated by the presence of branch points in the scintillated received wave fronts. In particular, correlation between the tilt and the projected beam's centroid error at the target has been observed in horizontal laser beam projection experiments. The presence of this correlation indicates that better tracking performance should be achievable. We compare the performance of four estimation schemes applied to tilt estimation in a horizontal laser projection system. It is demonstrated that all four schemes underestimate the tilt required to return the laser beam to a target in highly scintillated environments. A method of correcting this tilt is presented, and the expected performance improvement is quantified.