TUNABLE FILTER TECNIQUE :

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TUNABLE FILTER TECNIQUE

• A phase ambiguity solution with
  PYramid Phasing Sensor
• (PYPS)

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Technological development for the ELTs
ONE OF THE KEY ACTIVITIES
PHASING AND ALIGNMENT OF THE PRIMARY MIRROR
SEGMENTS
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Based on the sensing of phase step On the
segment edges
PYramid Phasing Sensor (PYPS)
limitation of signal ambiguity introduced by
the phase periodicity
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3 TECNIQUES THAT ALLOW TO SOLVE THE PHASE
AMBIGUITY WITH PYPS
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3 TECNIQUES THAT ALLOW TO SOLVE THE PHASE
AMBIGUITY WITH PYPS
-p
p
0
-p/2
p/2
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3 TECNIQUES THAT ALLOW TO SOLVE THE PHASE
AMBIGUITY WITH PYPS

-p
p
0
-p/2
p/2
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3 TECNIQUES THAT ALLOW TO SOLVE THE PHASE
AMBIGUITY WITH PYPS


-p
p
0
-p/2
p/2
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3 TECNIQUES THAT ALLOW TO SOLVE THE PHASE
AMBIGUITY WITH PYPS



-p
p
0
-p/2
p/2
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3 TECNIQUES THAT ALLOW TO SOLVE THE PHASE
AMBIGUITY WITH PYPS
Interaction matrix Reference acquisition (
requiredFIRST FLAT )
in order to operate in closed loop mode
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To obtain the condition in order to employed PYPS
in standard co-phasing tecnique
Piston error in /-l/2
C-loop calibration
New tecnique NO C-LOOP
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To obtain the condition in order to employed PYPS
in standard co-phasing tecnique
FIRST FLAT ACHIEVED!!!!
Piston error in /-l/2
C-loop calibration
FIRST FLAT CO-PHASING
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ABOUT WAVELENGHT SWEEP TECNIQUE
Based on piston signal dependence of the
wavelenght l
S S(1/l)
WE CAN USE A TUNABLE FILTER
Mesuring signal for several value of l
WE CAN FIT S(1/l)
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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.
Sheet polarizer
Lyot-type filter
quartz
Liquid crystal
Glass substrate
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2d
T is suppose to be positive we found
2d
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...future project about this tecnique is in APE
project and at the WHT collaboration with the WHT
group....
TUNABLE FILTER
ELTs
CO-PHASING
MAIN SCIENTIFIC CASES
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...future project about this tecnique is in APE
project and at the WHT collaboration with the WHT
group....
TUNABLE FILTER
ELTs
CO-PHASING
Exo-Planetary Systems and evolution
MAIN SCIENTIFIC CASES
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Liquid crystal tunable filter
Narrow-bandwith
Only wavelenght at which the ordinary and
extraordinary rays have optycal path lenghts
equal to an integer multyple of the wavelenght
exit the plates in the same polarization state as
they entered thje plates.
Uses electronically controlled liquid crystal
elements in a Lyot-type birefringent design to
select a transmitted wavelenght range while
blocking all others.
Sheet polarizer
Lyot-type filter
The separation and narrowness of the
transmission peacks depends on the number,
thickness,and orientation of the plates
quartz
Liquid crystal
There are multy-plate filters, and each plate
being half the thickness of the previous one.
Glass substrate
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Layot-filter Optical filter is composed of a
crystal birefrangent plane (usually quartz) that
is interposed bween two parallel polarizer
(inclined at 45 from optic axis of the
plate) 1)Wave hit the polarizator 2)Wave is
splitted in to two component ordinary an
extraordinary rays 3)The two waves component
have got different refraction index they are a
phase shift between (that dipends of plates
thickness and crystals birefringent) 4)The two
waves component are put together on the output
polarizator, and becouse of they inteference,
they realized a transmission 5)A series of these
layot-filter close each other allow us to select
the output wavelwnght.