“TUNABLE FILTER TECNIQUE :”

A phase ambiguity solution with PYramid Phasing Sensor (PYPS)

Technological development for the ELTs

ONE OF THE KEY ACTIVITIES: PHASING AND ALIGNMENT OF THE PRIMARY MIRROR SEGMENTS

ARE CORRECTEDSIMULTANEOUSLY

tiptilt

piston errorsof segmented mirror

Pyramid Wavefront Sensor: 2005

closed loop

PYramid Phasing Sensor (PYPS)Based on the sensing of phase step On the segment edges

!! !! limitation of signal ambiguity introduced by the phase periodicity

ambiguity

mirror surface step

wavelenght usedfor the sensing

PYPS signal

3 TECNIQUES THAT ALLOW TO SOLVE THE PHASE AMBIGUITY WITH PYPS

two wavelenght closed loop

wavelenght sweep tecnique (WST)

segment sweep tecnique (SST)

main task for an optical phasingmain task for an optical phasing sensor: to keep phased the segments sensor: to keep phased the segments during the observation during the observation PYPS

tip tilt piston errors correctionsimoultaneously

this has been done operating PYPS in closed loopsource nm

3 TECNIQUES THAT ALLOW TO SOLVE THE PHASE AMBIGUITY WITH PYPS

two wavelenght closed loop

wavelenght sweep tecnique (WST)

segment sweep tecnique (SST)

main task for an optica phasing sensormain task for an optica phasing sensor to keep phased the segments to keep phased the segments during the observation during the observation PYPS

tip tilt piston errors correctionsimoultaneously

this has been done operating PYPS in closed loopsource nm

open loop mode:open loop mode:sine function 22] not phase ambiguity

closed loop mode:closed loop mode: extended to ] around sinus zeroin this range the function of sin is preserved!

- ++2-2 0

3 TECNIQUES THAT ALLOW TO SOLVE THE PHASE AMBIGUITY WITH PYPS

two wavelenght closed loop

wavelenght sweep tecnique (WST)

segment sweep tecnique (SST)

main task for an optica phasing sensormain task for an optica phasing sensor to keep phased the segments to keep phased the segments during the observation during the observation PYPS

tip tilt piston errors correctionsimoultaneously

this has been done operating PYPS in closed loopsource nm

open loop mode:open loop mode:sine function 22] not phase ambiguity

closed loop mode:closed loop mode: extended to ] around sinus zeroin this range the function of sin is preserved!

- ++2-2 0

°

3 TECNIQUES THAT ALLOW TO SOLVE THE PHASE AMBIGUITY WITH PYPS

two wavelenght closed loop

wavelenght sweep tecnique (WST)

segment sweep tecnique (SST)

main task for an optica phasing sensormain task for an optica phasing sensor to keep phased the segments to keep phased the segments during the observation during the observation PYPS

tip tilt piston errors correctionsimoultaneously

this has been done operating PYPS in closed loopsource nm

open loop mode:open loop mode:sine function 22] not phase ambiguity

closed loop mode:closed loop mode: extended to ] around sinus zeroin this range the function of sin is preserved!

- ++2-2 0

°°

3 TECNIQUES THAT ALLOW TO SOLVE THE PHASE AMBIGUITY WITH PYPS

two wavelenght closed loop

wavelenght sweep tecnique (WST)

segment sweep tecnique (SST)

main task for an optica phasing sensormain task for an optica phasing sensor to keep phased the segments to keep phased the segments during the observation during the observation PYPS

tip tilt piston errors correctionsimoultaneously

this has been done operating PYPS in closed loopsource nm

open loop mode:open loop mode:sine function 22] not phase ambiguity

closed loop mode:closed loop mode: extended to ] around sinus zeroin this range the function of sin is preserved!

- ++2-2 0

°°

° The closed loop operation is able to drive the actuator to the same position(it works with iteraction process)

3 TECNIQUES THAT ALLOW TO SOLVE THE PHASE AMBIGUITY WITH PYPS

two wavelenght closed loop

wavelenght sweep tecnique (WST)

segment sweep tecnique (SST)

main task for an optica phasing sensormain task for an optica phasing sensor to keep phased the segments to keep phased the segments during the observation during the observation PYPS

tip tilt piston errors correctionsimoultaneously

this has been done operating PYPS in closed loopsource nm

Interaction matrixReference acquisition

( required:FIRST FLAT )

in order to operate in closed loop mode:

To obtain the condition in order to employed PYPS in standard co-phasing tecnique

Piston error in +/-

New tecnique : NO C-LOOP

Wavelenght Sweep Tecnique Segment Sweep Tecnique

Calibration NOT required

-> Segment are driven in to 500nm range (accuracy)

-> Capture range +/-13 m

-> parallel procedure

-> hight accuracy

-> capture range infinite

-> one segment as referenceAnd sweeping the neightbors

C-loop calibration

FAST!!!

To obtain the condition in order to employed PYPS in standard co-phasing tecnique

Piston error in +/-

FIRST FLAT CO-PHASING

Wavelenght Sweep Tecnique Segment Sweep Tecnique

Calibration NOT required

-> Segment are driven in to 500nm range (accuracy)

-> Capture range +/-13 m

-> parallel procedure

-> hight accuracy

-> capture range infinite

-> one segment as referenceAnd sweeping the neightbors

C-loop calibration

First m

ethod

Second method

FIRST FLAT ACHIEVED!!!!

ABOUT WAVELENGHT SWEEP TECNIQUE

Based on piston signal dependence of the wavelenght

S = S(1/)

Mesuring signal for several value of

WE CAN FIT S(1/)

this mesurement gives an extimation of the physical step that lies on the considered sensor sub-aperture

WE CAN USE A TUNABLE FILTER

Liquid crystal tunable filter

Narrow-bandwith

Uses electronically controlled liquid crystal elements in a Lyot-type birefringent design to select a transmitted wavelenght range while blocking all others.

quartz

Glass substrate

Liqu

id c

ryst

al

Sheet polarizer

Lyot-type filter

VARYNG THE GAP SELECT

ff fTf +P f

ff 2

++

WORKING LIMITS

the capture range is defined by the resolution of the wavelength sweep.

T is suppose to be positive we found : 2|d |

f

Minimum step:

m ~ 500 nm

Maximum step:

M ~ 80 m

1

The expected values for Pf are: 0 when d >0 when d <0

...future project about this tecnique is in APE project and at the WHT collaborationwith the WHT group....

TUNABLE FILTERTUNABLE FILTER ELTsELTsCO-PHASINGCO-PHASING

““MAIN SCIENTIFIC CASES”MAIN SCIENTIFIC CASES”

...future project about this tecnique is in APE project and at the WHT collaborationwith the WHT group....

TUNABLE FILTERTUNABLE FILTER ELTsELTsCO-PHASINGCO-PHASING

““MAIN SCIENTIFIC CASES”MAIN SCIENTIFIC CASES”

Exo-Planetary Systems and evolution

...future project about this tecnique is in APE project and at the WHT collaborationwith the WHT group....

TUNABLE FILTERTUNABLE FILTER ELTsELTsCO-PHASINGCO-PHASING

““MAIN SCIENTIFIC CASES”MAIN SCIENTIFIC CASES”

Exo-Planetary Systems and evolution

Star Formation and Stellar Discs

Dark Matte and Dark Energy

Galaxies and Cosmology

GRBs

Black Holes , AGNand QSOs

THE UNEXPECTED…….THE UNEXPECTED…….