Calibration and precompensation of noncommon path aberrations for extreme adaptive optics

Sauvage, Jean-François; Fusco, Thierry; Rousset, G.; Petit, Cyril

doi:10.1364/josaa.24.002334

Cited by 103 publications

(82 citation statements)

References 15 publications

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“…In particular, the contrast is improved by a factor that varies from 1.4 to 4.7 between 2λ/D and 15λ/D. We note that such a gain is superior to the one expected from SPHERE's baseline (classical phase diversity), which in addition, does not improve the contrast beyond 8λ/D (Sauvage et al 2012a). The origin of the contrast gain limitation observed here on the IRDIS camera is thoroughly studied in the next section.…”

Section: Contrast Optimization On Spherementioning

confidence: 60%

“…SPHERE's baseline currently relies on a differential estimation performed with phase diversity (Mugnier et al 2006;Sauvage et al 2012a), a focal plane wavefront sensing technique that uses classical imaging (no coronagraph). However, this wavefront sensor is limited to the estimation of aberrations up to eight cycles per pupil, which correspond to speckles close to the optical axis (up to a field angle of 8λ/D), whereas the SPHERE XAO system (SAXO) could compensate for up to 20 cycles per pupil.…”

Section: Introductionmentioning

confidence: 99%

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Compensation of high-order quasi-static aberrations on SPHERE with the coronagraphic phase diversity (COFFEE)

Paul

Sauvage

Mugnier

et al. 2014

A&A

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Context. The second-generation instrument SPHERE, dedicated to high-contrast imaging, will soon be in operation on the European Very Large Telescope. Such an instrument relies on an extreme adaptive optics system coupled with a coronagraph that suppresses most of the diffracted stellar light. However, the coronagraph performance is strongly limited by quasi-static aberrations that create long-lived speckles in the scientific image plane, which can easily be mistaken for planets. Aims. The wavefront analysis performed by SPHERE's adaptive optics system uses a dedicated wavefront sensor. The ultimate performance is thus limited by the unavoidable differential aberrations between the wavefront sensor and the scientific camera, which have to be estimated and compensated for. In this paper, we use the COFFEE approach to measure and compensate for SPHERE's quasi-static aberrations. Methods. COronagraphic Focal-plane waveFront Estimation for Exoplanet detection (COFFEE), which consists in an extension of phase diversity to coronagraphic imaging, estimates the quasi-static aberrations, including the differential ones, using only two focal plane images recorded by the scientific camera. In this paper, we use coronagraphic images recorded from SPHERE's infrared detector IRDIS to estimate the aberrations upstream of the coronagraph, which are then compensated for using SPHERE's extreme adaptive optics loop SAXO. Results. We first validate the ability of COFFEE to estimate high-order aberrations by estimating a calibrated influence function pattern introduced upstream of the coronagraph. We then use COFFEE in an original iterative compensation process to compensate for the estimated aberrations, leading to a contrast improvement by a factor that varies from 1.4 to 4.7 between 2λ/D and 15λ/D on IRDIS. The performance of the compensation process is also evaluated through simulations. An excellent match between experimental results and these simulations is found.

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Section: Contrast Optimization On Spherementioning

confidence: 60%

Section: Introductionmentioning

confidence: 99%

Compensation of high-order quasi-static aberrations on SPHERE with the coronagraphic phase diversity (COFFEE)

Paul

Sauvage

Mugnier

et al. 2014

A&A

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“…We then close the loop on the TS in SCAO mode on the internal calibration source. We measure the non common path aberrations (NCPA) between the TS iteratively with a phase diversity algorithm (see Sauvage et al 2007). We subtract their contribution, expressed in terms of slopes S NCPA , to the plane wavefront reference slopes to compute the final TS reference slopes:…”

Section: Reference Slopes Calibration and Dm Offsetmentioning

confidence: 99%

Analysis of on-sky MOAO performance of CANARY using natural guide stars

Vidal

Gendron

Rousset

et al. 2014

A&A

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The first on-sky results obtained by CANARY, the multi-object adaptive optics (MOAO) demonstrator, are analysed. The data were recorded at the William Herschel Telescope, at the end of September 2010. We describe the command and calibrations algorithms used during the run and present the observing conditions. The processed data are MOAO-loop engaged or disengaged slopes buffers, comprising the synchronised measurements of the four natural guide stars (NGS) wavefront sensors running in parallel, and near infrared (IR) images. We describe the method we use to establish the error budget of CANARY. We are able to evaluate the tomographic and the open loop errors, having median values around 216 nm and 110 nm respectively. In addition, we identify an unexpected residual quasi-static field aberration term of mean value 110 nm. We present the detailed error budget analysed for three sets of data for three different asterisms. We compare the experimental budgets with the numerically simulated ones and demonstrate a good agreement. We find also a good agreement between the computed error budget from the slope buffers and the measured Strehl ratio on the IR images, ranging between 10% and 20% at 1530 nm. These results make us confident in our ability to establish the error budget of future MOAO instruments.

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“…To take the DM action into account on the introduced phase (illustrated in Fig. 8), aberrations φ cal are first estimated with classical phase diversity (no phase mask in the coronagraphic focal plane, Sauvage et al 2007). This estimation gives us a calibration of the introduced aberration, which is then used to evaluate the accuracy of COFFEE's estimation.…”

Section: Ncpa Measurementsmentioning

confidence: 99%

“…4.2. Then, we use the pseudo-closed loop (PCL) method described in Sauvage et al (2007). This iterative process has two stages: for the PCL iteration i:…”

Section: Low-order Ncpa Compensationmentioning

confidence: 99%

Coronagraphic phase diversity: performance study and laboratory demonstration

Paul

Sauvage

Mugnier

2013

A&A

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Context. The final performance of current and future instruments dedicated to exoplanet detection and characterization (such as SPHERE on the European Very Large Telescope, GPI on Gemini North, or future instruments on Extremely Large Telescopes) is limited by uncorrected quasi-static aberrations. These aberrations create long-lived speckles in the scientific image plane, which can easily be mistaken for planets. Aims. Common adaptive optics systems require dedicated components to perform wave-front analysis. The ultimate wave-front measurement performance is thus limited by the unavoidable differential aberrations between the wave-front sensor and the scientific camera. To reach the level of detectivity required by high-contrast imaging, these differential aberrations must be estimated and compensated for. In this paper, we characterize and experimentally validate a wave-front sensing method that relies on focal-plane data. Methods. Our method, called COFFEE (for COronagraphic Focal-plane wave-Front Estimation for Exoplanet detection), is based on a Bayesian approach, and it consists in an extension of phase diversity to high-contrast imaging. It estimates the differential aberrations using only two focal-plane coronagraphic images recorded from the scientific camera itself. Results. We first present a thorough characterization of COFFEE's performance by means of numerical simulations. This characterization is then compared with an experimental validation of COFFEE using an in-house adaptive optics bench and an apodized Roddier & Roddier phase mask coronagraph. An excellent match between experimental results and the theoretical study is found. Lastly, we present a preliminary validation of COFFEE's ability to compensate for the aberrations upstream of a coronagraph.

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Calibration and precompensation of noncommon path aberrations for extreme adaptive optics

Cited by 103 publications

References 15 publications

Compensation of high-order quasi-static aberrations on SPHERE with the coronagraphic phase diversity (COFFEE)

Compensation of high-order quasi-static aberrations on SPHERE with the coronagraphic phase diversity (COFFEE)

Analysis of on-sky MOAO performance of CANARY using natural guide stars

Coronagraphic phase diversity: performance study and laboratory demonstration

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