Estimation of the adaptive optics long-exposure point-spread function using control loop data

Véran, Jean-Pierre; Rigaut, François; Maître, H.; Rouan, D.

doi:10.1364/josaa.14.003057

Cited by 180 publications

(186 citation statements)

References 13 publications

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“…It is also possible, as done at the Dunn telescope diameter (Marino et al 2004), to combine closed-loop wavefront sensor data with the control matrix and output voltages to estimate r 0 and residual low-order aberrations. The quality of such measurements are to some extent limited by time delays and inaccuracies in the control matrix, but experience with night-time AO systems clearly indicates that good PSF compensation is indeed possible with such data (Veran et al 1997). …”

Section: The Proposed Methodsmentioning

confidence: 99%

High-order aberration compensation with multi-frame blind deconvolution and phase diversity image restoration techniques

Scharmer

Löfdahl

Werkhoven

et al. 2010

A&A

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Context. For accurately measuring intensities and determining magnetic field strengths of small-scale solar (magnetic) structure, knowledge of and compensation for the point spread function is crucial. For images recorded with the Swedish 1-meter Solar Telescope (SST), restoration with multi-frame blind deconvolution (MFBD) and joint phase diverse speckle (JPDS) methods lead to remarkable improvements in image quality but granulation contrasts that are too low, indicating additional stray light. Aims. We propose a method to compensate for stray light from high-order atmospheric aberrations not included in MFBD and JPDS processing. Methods. To compensate for uncorrected aberrations, a reformulation of the image restoration process is proposed that allows the average effect of hundreds of high-order modes to be compensated for by relying on Kolmogorov statistics for these modes. The applicability of the method requires simultaneous measurements of Fried's parameter r 0 . The method is tested with simulations as well as real data and extended to include compensation for conventional stray light. Results. We find that only part of the reduction of granulation contrast in SST images is due to uncompensated high-order aberrations. The remainder is still unaccounted for and attributed to stray light from the atmosphere, the telescope with its re-imaging system and to various high-altitude seeing effects. Conclusions. We conclude that statistical compensation of high-order modes is a viable method to reduce the loss of contrast occurring when a limited number of aberrations is explicitly compensated for with MFBD and JPDS processing. We show that good such compensation is possible with only 10 recorded frames. The main limitation of the method is that already MFBD and JPDS processing introduces high-order compensation that, if not taken into account, can lead to over-compensation.

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Section: The Proposed Methodsmentioning

confidence: 99%

High-order aberration compensation with multi-frame blind deconvolution and phase diversity image restoration techniques

Scharmer

Löfdahl

Werkhoven

et al. 2010

A&A

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show abstract

“…Standard infrared data reduction techniques were then applied (sky subtraction, flat fielding and dead pixel correction). The images were also deconvolved using a PSF provided by the wave front sensor (Véran et al 1997). The deconvolution was a simple linear division by the MTF and filtering in the Fourier plane; the net effect of this deconvolution is mostly to reduce the halo produced by uncorrected seeing.…”

Section: Adaptive Opticsmentioning

confidence: 99%

The heterogeneous class ofλBootis stars

Gerbaldi

Faraggiana²,

Lai³

2003

A&A

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Abstract. We demonstrate that it is arduous to define the λ Boo stars as a class of objects exhibiting uniform abundance peculiarities which would be generated by a mechanism altering the structure of their atmospheric layers. We collected the stars classified as λ Boo up to now and discuss their properties, in particular the important percentage of confirmed binaries producing composite spectra (including our adaptive optics observations) and of misclassified objects. The unexplained RV variables (and thus suspected binaries), the known SB for which we lack information on the companion, the stars with an UV flux inconsistent with their classification, and the fast rotating stars for which no accurate abundance analysis can be performed, are also reviewed.

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“…The scheme proposed in this article is a form of adaptive optics PSF reconstruction, which uses measurements acquired in a wavefront sensor to estimate the long-exposure PSF in the science camera (Veran et al 1997;Gendron et al 2006). Adaptive optics PSF reconstruction has been implemented on several adaptive optics systems (Harder & Chelli 2000;Jolissaint et al 2010) and relies on the fact that the wavefront sensor, by measuring residual wavefront errors at a fixed spatial sampling, can be used to estimate the inner part of the PSF in the science camera.…”

Section: Clowfs Postprocessing Principlementioning

confidence: 99%

Coronagraphic Low-Order Wavefront Sensor: Postprocessing Sensitivity Enhancer for High-Performance Coronagraphs

Vogt

Martinache

Guyon

et al. 2011

Publications of the Astronomical Society of the Pacific

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ABSTRACT. Detection and characterization of exoplanets by direct imaging requires a coronagraph designed to deliver high-contrast at small angular separation. To achieve this, an accurate control of low-order aberrations, such as pointing and focus errors, is essential to optimize coronagraphic rejection and avoid the possible confusion between exoplanet light and coronagraphic leaks in the science image. Simulations and laboratory prototyping have shown that a coronagraphic low-order wavefront sensor (CLOWFS), using a single defocused image of a reflective focal-plane ring, can be used to control tip-tilt to an accuracy of 10 À3 λ=D. This article demonstrates that the data acquired by CLOWFS can also be used in postprocessing to calibrate residual coronagraphic leaks from the science image. Using both the CLOWFS camera and the science camera in the system, we quantify the accuracy of the method and its ability to successfully remove light due to low-order errors from the science image. We also report the implementation and performance of the CLOWFS on the Subaru Coronagraphic Extreme-AO (SCExAO) system and its expected on-sky performance. In the laboratory, with a level of disturbance similar to that encountered in a post-AO beam, CLOWFS postprocessing has achieved speckle calibration to 1=300 of the raw speckle level. This is about 40 times better than could be done with an idealized PSF subtraction that does not rely on CLOWFS.

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Estimation of the adaptive optics long-exposure point-spread function using control loop data

Cited by 180 publications

References 13 publications

High-order aberration compensation with multi-frame blind deconvolution and phase diversity image restoration techniques

High-order aberration compensation with multi-frame blind deconvolution and phase diversity image restoration techniques

The heterogeneous class ofλBootis stars

Coronagraphic Low-Order Wavefront Sensor: Postprocessing Sensitivity Enhancer for High-Performance Coronagraphs

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