Practical issues with phase diversity for NCPA compensation resolved on the CANARY demonstrator
Abstract
Phase diversity (PD) for non common path aberration retrieval and compensation is mainly limited by the accuracy of the AO bench calibration in the image plane: pupil model (shape, size and illumination), IR camera pixel size, deformable mirror influence functions geometrical model. Some of these issues can be treated numerically from classical PD data but with limited accuracy and implying large use of the bench and large amount of computational resources. We propose a new fast and practical approach based on the combination of a simplified optical setup and an empirical numerical model to perform these calibrations with high accuracy. This approach has been tested successfully using a NICMOS-based IR camera: CAMICAz, installed on the CANARY MOAO demonstrator and allowed us to increase significantly image quality in the near-IR. Additionally, some authors have proposed to use long exposure phase diversity to sense online the quasi-static aberrations under partial AO correction on sky. Applying our practical approach in this context and using an original image formation model, we were able to reach on sky the same level of static aberration compensation, independently and assuming no pre-compensation from lab measurements, leading to a significant increase of on-sky performance.
- Publication:
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Proceedings of the Third AO4ELT Conference
- Pub Date:
- December 2013
- DOI:
- 10.12839/AO4ELT3.13325
- Bibcode:
- 2013aoel.confE..67G
- Keywords:
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- Data post-processing & optimization