Context :

Aims : We present ground-based observations of the disk around the A-type star \beta Pictoris to obtain scattered light images at the highest angular resolution ( 60 mas , equivalent to about 1 AU at the distance of the star ) and the highest contrast in the very close environment of the star .
The purpose of this program is to perform a close inspection of the inner disk morphology .

Methods : Images were collected with NACO , the AO-assisted near-IR instrument on the VLT ( ESO ) which includes two types of coronagraphs : classical Lyot masks and phase masks .
In this program we took advantage of both types of coronagraphs in two spectral bands , H-band for the Lyot mask and Ks-band for the phase mask .
The Lyot mask blocks a large central region around the star ( radius < 0.35 ” ) but allows deep integrations and hence good signal-to-noise ratio at large distances , while the phase mask allows imaging at very close separation ( down to \sim 0.15 ” in theory ) but conversely is more sensitive to residual aberrations .
In addition , we simulated an extended object to understand the limitations in deconvolution of coronagraphic images .

Results : The reduced coronagraphic images allow us to carefully measure the structures of the debris disk and reveal a number of asymmetries of which some were not reported before ( position , elevation and thickness of the warp ) .
Our analysis also demonstrates the advantage of the phase mask coronagraph to explore the very close environment of stars .
In this program , the circumstellar material is visible as close as 0.7 ” ( 13.5 AU ) owing to the phase mask while the Lyot mask generates artifacts which hamper the detection of the dust at separations closer than 1.2 ” ( 23.2 AU ) .
The point source detection limit is compared to recently published observations of a planet candidate .
Finally , the simulations show that deconvolution of coronagraphic data may indeed produce artificial patterns within the image of a disk .

Conclusions :