%0 Journal Article %T Peak-locking centroid bias in Shack-Hartmann wavefront sensing %+ Laboratoire d'Astrophysique de Marseille (LAM) %A Anugu, Narsireddy %A Garcia, Paulo J. V. %A Correia, Carlos M. %< avec comité de lecture %@ 0035-8711 %J Monthly Notices of the Royal Astronomical Society %I Oxford University Press (OUP): Policy P - Oxford Open Option A %V 476 %P 300-306 %8 2018 %D 2018 %Z 1801.06836 %Z 2018MNRAS.476..300A %R 10.1093/mnras/sty182 %K instrumentation: adaptive optics %K techniques: high angular resolution %K techniques: image processing %K Astrophysics - Instrumentation and Methods for Astrophysics %Z Sciences of the Universe [physics] %Z Sciences of the Universe [physics]/Astrophysics [astro-ph]Journal articles %X Shack-Hartmann wavefront sensing relies on accurate spot centre measurement. Several algorithms were developed with this aim, mostly focused on precision, i.e. minimizing random errors. In the solar and extended scene community, the importance of the accuracy (bias error due to peak-locking, quantization, or sampling) of the centroid determination was identified and solutions proposed. But these solutions only allow partial bias corrections. To date, no systematic study of the bias error was conducted. This article bridges the gap by quantifying the bias error for different correlation peak-finding algorithms and types of sub-aperture images and by proposing a practical solution to minimize its effects. Four classes of sub-aperture images (point source, elongated laser guide star, crowded field, and solar extended scene) together with five types of peak-finding algorithms (1D parabola, the centre of gravity, Gaussian, 2D quadratic polynomial, and pyramid) are considered, in a variety of signal-to-noise conditions. The best performing peak-finding algorithm depends on the sub-aperture image type, but none is satisfactory to both bias and random errors. A practical solution is proposed that relies on the antisymmetric response of the bias to the sub-pixel position of the true centre. The solution decreases the bias by a factor of ∼7 to values of ≲ 0.02 pix. The computational cost is typically twice of current cross-correlation algorithms. %G English %2 https://insu.hal.science/insu-03666270/document %2 https://insu.hal.science/insu-03666270/file/sty182.pdf %L insu-03666270 %U https://insu.hal.science/insu-03666270 %~ INSU %~ CNRS %~ UNIV-AMU %~ CNES %~ LAM %~ OSU-INSTITUT-PYTHEAS