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Astron. Astrophys. 350, L23-L26 (1999)

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Letter to the Editor

Sensitivity of a pyramidic Wave Front sensor in closed loop Adaptive Optics

R. Ragazzoni 1 and J. Farinato 2

1 Astronomical Observatory of Padova, vicolo dell'Osservatorio 5, 35122 Padova, Italy (ragazzoni@pd.astro.it)
2 European Southern Observatory, Karl-Schwarzschild-Strasse 2, 83702 Garching bei München, Germany (jfarinat@eso.org)

Received 17 June 1999 / Accepted 17 August 1999


The Pyramidic wavefront has a very interesting property: its SNR has a significant increase once the loop is closed, similarly to the Curvature Sensor and contrasting with the Shack-Hartmann one. This result in a gain comparing the Pyramidic and the Shack-Hartmann sensors. It is shown by a combination of descriptive and numerical arguments that this gain is of the order of [FORMULA] for low order modes and drift linearly down to the Shack-Hartmann case at the highest spatial frequency sampled. A discussion of the overall gain (including a first estimation of the magnitude gain) and procedures to force a true system to work in closed loop fashion are sketched.

Key words: telescopes – instrumentation: adaptive optics

© European Southern Observatory (ESO) 1999

Online publication: October 4, 1999