摘要：Aims. This article describes the implementation of a focal plane based
wavefront control loop on the high-contrast imaging instrument SCExAO (Subaru
Coronagraphic Extreme Adaptive Optics). The sensor relies on the Fourier analysis of
conventional focal-plane images acquired after an asymmetric mask is introduced in the
pupil of the instrument.
Methods. This absolute sensor is used here in a closed-loop to
compensate for the non-common path errors that normally affects any imaging system relying
on an upstream adaptive optics system.This specific implementation was used to control
low-order modes corresponding to eight zernike modes (from focus to spherical).
Results. This loop was successfully run on-sky at the Subaru Telescope
and is used to offset the SCExAO deformable mirror shape used as a zero-point by the
high-order wavefront sensor. The paper details the range of errors this wavefront-sensing
approach can operate within and explores the impact of saturation of the data and how it
can be bypassed, at a cost in performance.
Conclusions. Beyond this application, because of its low hardware
impact, the asymmetric pupil Fourier wavefront sensor (APF-WFS) can easily be ported in a
wide variety of wavefront sensing contexts, for ground- as well space-borne telescopes,
and for telescope pupils that can be continuous, segmented or even sparse. The technique
is powerful because it measures the wavefront where it really matters, at the level of the
science detector.
关键词：instrumentation: adaptive optics;methods: data analysis;techniques: high angular resolution;techniques: interferometric
