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Pyramid sensors for AO and co-phasing. Two key projects in Arcetri AO groups for 8m class telescopes and ELT wavefront sensing: -WFS for LBT AO system -Segment co-phasing for EELT. PS. SH. Pyramid WFS in Adaptive Optics.

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Pyramid sensors for ao and co phasing

Pyramid sensors for AO and co-phasing

Two key projects in Arcetri AO groups for 8m class telescopes and ELT wavefront sensing:

-WFS for LBT AO system

-Segment co-phasing for EELT

Pyramid wfs in adaptive optics



Pyramid WFS in Adaptive Optics

A Strehl Ratio plot (peak value of the corrected PSF normalized to peak value for perfect correction) as a function of guide star magnitude in R band for Pyramid Sensor (PS) and Shack-Hartmann sensor (SH).

PS is less sensitive to uncorrected

atmospheric perturbations. Energy

left In the PSF halo is 1/3 for PS.

Enabling higher PSF contrast.

PS achieve same performance

With a star about 2 mag fainter.

AO system sky coverage is


Strehl Ratio in seeing

limited case (8m tel.)

Ao system for lbt
AO system for LBT

  • -An astronomical AO system with two key components:

    • 1) DM: a deformable secondary with 672 actuators.

    • 2) Sensor: a pyramid WFS with up to 30x30 subapertures.

  • -AO system coupled to 1-2.5 mm DL imager & spectrograph LUCIFER

  • the main LBT instrument for diffraction limited observations

  • Project main dates:

    • -AO #1 comm. date: Dec08

    • -AO #2 comm. date: Sep09

FLAO on LBT telescope

The secondary unit

The pyramid WFS unit

A closer view to wfs unit

Acquisition & guiding AG unit

Wavefront sensing W unit

A closer view to WFS unit

The WFS board during integration

The glass pyramid


Closed loop lab test of the ao system

WFS unit

The lab set-up for AO system test

Closed loop lab test of the AO system

45-actuator prototype

The 45 actuators prototype

of deformable secondary

Segment co phasing for the elt
Segment co-phasing for the ELT

Arcetri AO group demonstrated that the Pyramid sensor can detect simultaneously

segment differential piston as well as tip and tilt of the segments.

-A single WFS for segmented mirror alignment

-A single WFS for co-phasing and AO

Closed loop alignment

of the segmented DM

of NAOMI AO system @ WHT


Piston signals, (X,Y)

Tip tilt rms

Piston rms

Tilt signals (X,Y)

The active Phasing Experiment (APE)

Active Phasing Experiment (APE) is the WP4600

of the ELT Design Study. Experiment is aimed to

realize , test and compare three co-phasing

Sensor in lab at ESO and at the VLT.

Initial rms > λ/2

Co-phasing loop:

Start 110nm rms

Stop 12nm rms

Final rms 23nm

New projects
New projects:

LGS GLAO system for LBT

A project to provide LBT with a Laser Guide Star Ground Layer AO system is started as phase A study in May07. The program has an upgrade path aimed to extend GLAO system to LGS diffraction limited AO for imaging on small FoV.

-GLAO system will be coupled with the multi-object spectroscopic unit of LUCIFER having a 4x2 arcmin FoV.

MCAO for EELT phase A study


Oss. Ast.


A 2 years phase A study to analize

the design of a Multi-Conjugate AO

system for the EELT leaded by

Osservatorio di Bologna (OAB).